Such experiences clearly show that the same anomaly may occur in different species, and no doubt in strains of the same species from different localities, according to at least two different standards. The one is to be called the poor, and the other the rich variety. The first always produces relatively few instances of the deviation, the last is apt to give as many of them as desired. The first is only half-way a variety, and therefore would deserve the name of a half-race; the second is not yet a full constant variety, but always fluctuates to and fro between the varietal and the specific mark, ever-sporting in both directions. It holds a middle position between a half-race and a variety, and therefore might be called a "middle-race." But the term ever-sporting variety seems more adequate to convey a right idea of the nature of this curious type of inheritance.

From this discussion it will be seen that the behavior of the crimson clover is not to be considered [359] as an exception, but as a widely occurring type of phenomenon, occurring perhaps in all sorts of teratologic deviations, and in wide ranges of species and genera. Hence it may be considered worth while to give some more details of this extended experiment.

Ten years ago (1894-5) I bought and sowed about a pound of seed of the crimson clover. Among many thousands of normal seedlings I found two with three and one with four cotyledons. Trusting to the empirical rules of correlation, I transplanted these three individuals in order to isolate them in the flowering period.

One of them produced during the ensuing summer one four-bladed and one five-bladed leaf. The seeds were saved separately and sown the following spring and the expected result could soon be seen. Among some 250 individual plants I counted 22 with one or two deviations, and 10 with from three to nine four- or five-bladed leaves. Proportions nearly similar have been observed repeatedly. Better nourished individuals have produced more deviating leaves on one plant, partly owing to the larger number of stems and branches, and poor or average specimens have mostly been without any aberration or with only one or two abnormal leaves. No further improvement could be attained. Quadrifoliolate leaves were always rare, never [360] attaining a number that would put its stamp on a whole bed. I have endeavored to get some six- and seven-bladed crimson clover leaves, but in vain; selection, culture of many hundreds of individuals, manure, and the best possible treatment has not been adequate to produce them. Of course I am quite convinced that a repetition of my experiment on a far larger scale would yield the desired types, but then only in such rare instances that they would have no influence whatever on the average, or on the improvement of the race. The eighth generation in the year 1903 has not been noticeably better than the second and third generations after the first selection.

In comparing this statement with the results gained in the experiment with the red clover, the difference is at once striking. In one case a rich variety was isolated, and, by better treatment and sharp methods of selection, was brought up in a few years to its highest pitch of development. In the other case a very weak race was shown to exist, and no amount of work and perseverance was adequate to improve it to any noticeable degree.

I wish to point out that the decision of what is to be expected from deviating specimens may become manifest within one or two generations. Even the generation grown from the seeds of [361] the first observed aberrant-individuals, if gathered after sufficient isolation during the period of blossoming, may show which type of inheritance is present, whether it is an unpromising half-race, or a richly endowed sporting variety. I have kept such strains repeatedly after the first isolation, and a special case, that of cotyledoneous aberrations, will be dealt with later. The first generation always gave a final decision, provided that a suitable method of cultivation for the species under observation was found at the beginning. This however, is a condition, which it is not at all easy to comply with, when new sorts are introduced into a garden. Especially so when they had been collected in the wild state. Often one or two years, sometimes more, are necessary to find the proper method of sowing, manuring, transplanting and, other cultural methods satisfactory to the plants. Many wild species require more care and more manure in gardens than the finest garden flowers. And a large number are known to be dependent on very particular conditions of soil.

One of the most curious features of anomalies, which has been learned from accumulated instances, is the fact that they obey definite laws as to their occurrence on the different parts of the plant. Obviously such laws are [362] not apparent as long as each plant produces only one or two, or, at most, a few instances of the same deviation. On the contrary, any existing regularity must betray itself, as soon as a larger number of instances is produced. A rule of periodicity becomes most clearly manifest in such cases.

This rule is shown by no other race in a more undoubted and evident manner than by the "five-leaved" clover. Evidently the several degrees of deviation, going from three to seven leaflets, may be regarded as responses to different degrees of variation, and their distribution over the stems and branches, or over the whole plant, may be considered as the manifestation of the ever-changing internal tendency to vary.

Considered from this point of view, my plants always showed a definite periodicity in this distribution, which is the same for the whole plant. Each of them, and each of the larger branches, begin with atavistic leaves or with slight deviations. These are succeeded by greater deviations, but only the strongest axes show as many as seven leaflets on a stalk. This ordinarily does not occur before the height of development is reached, and often only towards its close. Then the deviation diminishes rapidly, returning often to atavistic leaves at the summit of the stem or branch. I give the numbers of the [363] leaves of a branch, in their order from the base to the top. They were as follows:

3. 4. 5. 6. 7. 5. 5. 4.

But this is a selected case, and such regular examples of the expected periodicity are rarely found. Often one or more of the various steps are lacking, or even leaves with smaller numbers may be interspersed among those with larger numbers of leaflets. But while the regularity of the periodicity is in some degree diminished by such occurrences, yet the rule always holds good, when taken broadly. It may be expressed by stating that the bases and apices have on the average fewer leaflets on each leaf than the middle parts of the stem and branches, and that the number of leaflets gradually increases from the base toward a maximum, which is reached in organs on the middle or upper part of the axis, and then diminishes from this toward the apex.

This periodicity is not limited to the stems and branches, considered singly, but also holds good in a comparison made between the branches of a single stem, in regard to their relative places on that stem. So it is also for the whole plant. The first stems, produced by the subterranean axis, ordinarily show only a low maximum deviation: the next succeeding being [364] more divergent and the last ones returning to less differentiated forms.

It is evident that on a given stem the group of deviating leaves will be extended upward and downward, with the increase of the number of these organs. This shows that a stem, or even a plant, promises a higher degree of differentiation if it commences with its aberration earlier. Hence it becomes possible to discern the most promising individuals in early youth, and this conclusion leads to a very easy and reliable method of selection, which may be expressed simply as follows: the seedlings which commence earliest with the production of four- and five-foliolate leaves are the best and should be selected for the continuance of the race. And it is easily seen that this rule agrees with that given above, and which was followed in my pedigree-culture.

Furthermore it is seen that there is a complete agreement between the law of periodicity and the responses of the deviations to nourishment and other conditions of life. Weak plants only produce low degrees of deviation, the stronger the individual becomes, the higher it reaches in the scale of differentiation, and the more often it develops leaves with five or more blades. Whether weakness or strength are derived from outer causes, or from the internal [365] succession of the periods of life, is evidently of no consequence, and in this way the law of periodicity may be regarded as a special instance of the more general law of response to external conditions.

The validity of this law of periodicity is of course not limited to our "five-leaved" clover. Quite on the contrary it is universal in eversporting varieties. Moreover it may be ascertained and studied in connection with the most widely different morphologic abnormalities, and therefore affords easily accessible material for statistical inquiry. I will now give some further instances, but wish to insist first upon the necessity of an inquiry on a far larger scale, as the evidence as yet is very scanty.

The great celandine (Chelidonium majus) has a very curious double variety. Its flowers are simpler and much more variable than in ordinary garden-varieties. The process of doubling consists mainly in a change of stamens into petals. This change is dependent on the season. On each stem the earliest flowers are single. These are succeeded by blossoms with one or two converted stamens, and towards the summer this number increases gradually, attaining 10-11 and in some instances even more altered filaments. Each year the same succession may be seen repeating itself on the stems of [366] the old roots. Double tuberous begonias are ordinarily absolutely sterile throughout the summer, but towards autumn the new flowers become less and less altered, producing some normal stamens and pistils among the majority of metamorphosed organs. From these flowers the seeds are saved. Sometimes similar flowers occur at the beginning of the flowering-period. Double garden-camomiles (Chrysanthemum inodorum plenissimum) and many other double varieties of garden-plants among the great family of the composites are very sensitive to external agencies, and their flower-heads are fuller the more favorable the external conditions. Towards the autumn many of them produce fewer and fewer converted heads and often only these are fertile and yield seeds.

Ascidia afford another instance of this periodicity, though ordinarily they are by far too rare to show any regularity in their distribution. However, it is easy to observe that on lime-trees they prefer the lower parts of each twig, while on magnolias the terminal leaves of the branches are often pitcher-bearing. Ascidia of the white clover have been found in numbers, in my own experiment-garden, but always in the springtime. The thickleaved saxifrage (Saxifraga crassifolia) is often very productive of ascidia, especially in [367] the latter part of the season, and as these organs may be developed to very different degrees, they afford fine material for the study of the law of periodicity. On a garden-cytisus (Cytisus candicans attleyanus) I once had the good fortune to observe a branch with ascidia, which ordinarily are very rare in this species. It had produced seven ascidia in all, each formed by the conversion of one leaflet on the trifoliolate leaves. The first six leaves were destitute of this malformation and were quite normal. Then followed a group of five leaves, constituting the maximum of the period. The first bore one small pitcher-like blade, the second and third, each one highly modified organ, the fourth, two ascidia, and the last, one leaflet with slightly connate margins. The whole upper part of the branch was normal, with the exception of the seventeenth leaf, which showed a slight change in the same direction. All in all, the tendency to produce ascidia increased from the beginning to the tenth leaf, and decreased from this upward.

The European Venus' looking-glass was observed in my garden to produce some quaternate and some quinate flowers on the same specimens. The quinate were placed at the end of the branches, those with four petals and sepals lower down. The peloric fox-glove shows the [368] highest degree of metamorphy in the terminal flowers of the stem itself, the weaker branches having but little tendency towards the formation of the anomaly. The European pine or Pinus sylvestris ordinarily has two needles in each sheath, but trifoliolate sheaths occur on the stems and stronger branches, where they prefer, as a rule, the upper parts of the single annual shoots. Camellia japonica is often striped in the fall and during the winter, but when flowering in the spring it returns to the monochromatic type.

Peloric flowers are terminal in some cases, but occur in the lower parts of the flower-spikes in others. Some varieties of gladiolus commence on each spike with more or less double flowers, which, higher up, are replaced by single ones. A wide range of bulbs and perennial garden-plants develop their varietal characters only partly when grown from seed and flowering for the first time. The annual garden-forget-me-not of the Azores (Myosotis azorica) has a variety with curiously enlarged flowers, often producing 20 or more corolla-segments in one flower. But this number gradually diminishes as the season advances. It would be quite superfluous to give further proof of the general validity of the law of periodicity in ever-sporting varieties.

[369]

LECTURE XIII

PISTILLODY IN POPPIES

One of the most curious anomalies that may be met with in ornamental garden-plants is the conversion of stamens into pistils. It is neither common nor rare, but in most cases the change is so slight comparatively that it is ordinarily overlooked. In the opium-poppy, on the contrary, it is very showy, and heightens the ornamental effect of the young fruits after the fading of the flowers. Here the central capsule is surrounded by a large crown of metamorphosed stamens.

This peculiarity has attracted the attention both of horticulturists and of botanists. As a rule not all the stamens are changed in this way but only those of the innermost rows. The outer stamens remain normal and fertile, and the flowers, when pollinated with their own pollen, bear as rich a harvest of seeds as other opium-poppies. The change affects both the filament and the anther, the former of which is dilated into a sheath. Within this sheath perfect [370] and more or less numerous ovules may be produced. The anthers become rudimentary and in their place broad leafy flaps are developed, which protrude laterally from the tip and constitute the stigmas. Ordinarily these altered organs are sterile, but in some instances a very small quantity of seed is produced, and when testing their viability I succeeded in raising a few plants from them.

The same anomaly occurs in other plants. The common wall-flower (Cheiranthus Cheiri) and the houseleek (Sempervivum tectorum) are the best known instances. Both have repeatedly been described by various investigators. In compiling the literature of this subject it is very interesting to observe the two contrasting views respecting the nature of this anomaly. Some writers, and among them Masters in his "Vegetable Teratology" consider the deviations to be merely accidental. According to them some species are more subject to this anomaly than others, and the houseleek is said to be very prone to this change. Goeppert, Hofmeister and others occasionally found the pistilloid poppies in fields or gardens, and sowed their seeds in order to ascertain whether the accidental peculiarity was inheritable or not. On the other hand De Candolle in his "Prodromus" mentions the pistilloid wall-flowers as a distinct [371] variety, under the name of Cheiranthus Cheiri gynantherus, and the analogous form of the opium-poppy is not at all an accidental anomaly, but an old true horticultural variety, which can be bought everywhere under the names of Papaver somniferum monstruosum or polycephalum. Since it is an annual plant, only the seeds are for sale, and this at once gives a sufficient proof of its heredity. In all cases, where it was met with accidentally by botanists, it is to be assumed that stray seeds had been casually mixed with those of other varieties, or that the habit had been transmitted by a spontaneous cross.

Wherever opportunity led to experiments on heredity, distinct races were found to be in possession of this quality, while others were not. It is of no use to cultivate large numbers of wall-flowers in the hope of one day seeing the anomaly arise; the only means is to secure the strain from those who have got it. With poppies the various varieties are so often intercrossed by bees, that the appearance of an accidental change may sometimes be produced, and in the houseleek the pistilloid warily seems to be the ordinary one, the normal strain being very rare or perhaps wholly wanting.

Our three illustrative examples are good and permanent races, producing their peculiar qualities [372] regularly and abundantly. In this respect they are however very variable and dependent on external circumstances. Such a regularity is not met with in other instances. Often pedigree-experiments lead to poor races, betraying their tendency to deviate only from time to time and in rare cases. Such instances constitute what we have called in a former lecture, "half races," and their occurrence indicates that the casual observation of an anomaly is not in itself adequate to give an opinion as to the chance of repetition in sowing experiments. A large number of species seem to belong to this case, and their names may be found in the above mentioned work by Masters and elsewhere. But no effort has yet been made to separate thoroughly the pistilloid half-races from the corresponding ever-sporting varieties. Some plants are recorded as being more liable to this peculiarity than others.

Stamens are sometimes replaced by open carpels with naked ovules arising from their edges and even from their whole inner surfaces. This may be seen in distinct strains of the cultivated bulbous Begonia, and more rarely in primroses. Here the apex of the carpellary leaf is sometimes drawn out into a long style, terminated by a flattened spatulate stigma.

The pistillody of the stamens is frequently [373] combined with another deviation in the poppies. This is the growing together of some of the altered stamens so as to constitute smaller or larger connate groups. Often two are united, sometimes three, four or more. Flowers with numerous altered stamens are seldom wholly free from this most undesirable secondary anomaly. I call it undesirable with respect to experiments on the variability of the character. For it may easily be seen that while it is feasible to count the stamens even when converted into pistils, it is not possible when groups of them are more or less intimately united into single bodies. This combination makes all enumeration difficult and inaccurate and often wholly unreliable. In such cases the observation is limited to a computation of the degree of the change, rather than to a strict numerical inquiry. Happily the responses to the experimental influences are so marked and distinct that even this method of describing them has proved to be wholly sufficient.

In extreme instances I have seen all the changed stamens of a flower of the opium-poppy united into a single body, so as to form a close sheath all around the central ovary. Lesser sheaths, surrounding one-half or one-third of the capsule are of course less rarely met with. Leaving this description of the outer appearance [374] of our anomaly, we may now consider it from the double point of view of inheritance and variability.

The fact of inheritance is shown by the experience of many authors, and by the circumstance already quoted, that the variety has been propagated from seed for more than half a century, and may be obtained from various seed merchants. In respect to the variability, the variety belongs to the ever-sporting group, constituting a type which is more closely related to the "five-leaved" clover than to the striped flowers or even the double stocks.

It fluctuates around an average type with half filled crowns, going as far as possible in both directions, but never transgressing either limit. It is even doubtful whether the presumable limits are, under ordinary circumstances, ever reached. Obviously one extreme would be the conversion of all the stamens, and the other the absolute deficiency of any marked tendency to such a change. Both may occur, and will probably be met with from time to time. But they must be extremely rare, since in my own extensive experiments, which were strictly controlled, I never was able to find a single instance of either of them. Some of the outer stamens have always remained unchanged, yielding enough pollen for the artificial pollination of [375] the central ovary, and on the other hand some rudiments of hardened filaments were always left, even if they were reduced to small protuberances on the thalamus of the flower. Between these extremes all grades occur. From single, partially or wholly changed stamens upwards to 150 and over, all steps may be seen. It is a true fluctuating variability. There is an average of between 50 and 100, constituting a nearly filled crown around the central capsule. Around this average the smaller deviations are most numerous and the larger ones more rare. The inspection of any bed of the variety suffices to show that, taken broadly, the ordinary laws of fluctuating variability are applicable. No counting of the single individuals is required to dispel all doubts on this point.

Moreover all intermediate steps respecting the conversion of the single stamens may nearly always be seen. Rarely all are changed into normal secondary ovaries with a stigma and with a cavity filled with ovules. Often the stigma is incomplete or even almost wanting, in other instances the ovules are lacking or the cavity itself is only partially developed. Not rarely some stamens are reduced and converted into thin hard stalks, without any appearance of an ovary at their tip. But then the demarcation [376] between them and the thalamus fails, so that they cannot be thrown off when the flower fades away, but remain as small stumps around the base of the more fully converted filaments. This fact would frequently render the enumeration of the altered organs quite unreliable.

For these reasons I have chosen a group of arbitrary stages in order to express the degree of deviation for a given lot of plants. The limits were chosen so as to be sufficiently trustworthy and easy to ascertain. In each group the members could be counted, and a series of figures was reached by this means which allowed of a further comparison of the competing sets of plants.

It should be stated that in such experiments and especially in the case of such a showy criterion as the pistilloid heads afford after the time of flowering is over, the inspection of the controlling beds at once indicates the result of the experiment. Even a hasty survey is in most cases sufficient to get a definite conclusion. Where this is not the case, the counting of the individuals of the various groups often does not add to the evidence, and the result remains uncertain. On the other hand, the impression made by the groups of plants on the experimenter and on his casual visitors, cannot well be conveyed to the readers of his account by [377] other means than by figures. For this reason the result of the experiments is expressed in this way.

I made six groups. The first includes the cases where the whole circle is reduced to small rudiments. The second shows 1-10 secondary capsules. The two following constitute half a crown around the central fruit, the third going up to this limit, the fourth going from this limit to a nearly filled circle. Wholly filled circles of secondary capsules without gaps give the two last degrees, the fifth requiring only continuity of the circle, the sixth displaying a large and bright crown all around the central head. The fifth group ordinarily includes from 90-100 altered stamens, while the sixth has from 100-150 of these deviating parts.

In ordinary cultures the third and fourth group, with their interrupted crowns, predominate. Large crowns are rare and flowers which at first sight seem to be wholly normal, occur only under circumstances definitely known to be unfavorable to growth, and to the development of the anomaly.

Having reached by this means a very simple and easy method of stating the facts shown by equal lots under contrasting influences, we will now make use of it to inquire into the relation [378] of this exceptionally high degree of variability to the inner and outer conditions of life.

As a rule, all experiments show the existence of such a relation. Unfavorable conditions reduce the numbers of altered stamens, favorable circumstances raise it to its highest point. This holds true for lots including hundreds of specimens, but also for the sundry heads of one bed, and often for one single plant.

We may compare the terminal flower with those of the lateral branches on a plant, and when no special influences disturb the experiment, the terminal head ordinarily bears the richest crown. If the first has more than 100 metamorphosed parts, the latter have often less than 50 on the same plant. In poor soil, terminal heads are often reduced to 10-20 monstrous organs, and in such cases I found the lateral flowers of the same plants ordinarily with less than 10 altered stamens. In some cases I allowed the branches of the third and fourth degree, in other words, the side twigs of the first branches of my selected plants to grow out and produce flowers in the fall. They were ordinarily weak, sometimes very small, having only 5-9 stigmas on their central fruit. Secondary capsules were not seen on such flowers, even when the experiment was repeated on a [379] somewhat larger scale and during a series of years.

Among the same lot of plants individual differences almost always occur. They are partly due to inequalities already existing in the seeds, and partly to the diversity of the various parts of the same bed. Some of the plants become stout and have large terminal heads. Others remain very weak, with a slender stem, small leaves and undersized flowers. The height and thickness of the stem, the growth of the foliage and of the axillary buds are the most obvious measures of the individual strength of the plant. The development of the terminal flower and the size of its ovary manifestly depends largely on this individual strength, as may be seen at once by the inspection of any bed of opium-poppies. Now this size of the head can easily be measured, either by its height or circumference, or by its weight. Moreover we can arrange them into a series according to their size. If we do this with the polycephalous variety, the relation between individual strength and degree of metamorphosis at once becomes manifest. The largest heads have the brightest crowns, and the number of supernumerary carpels diminishes in nearly exact proportion to the size of the fruits. Fruits with less than 50 altered stamens weighed on an average 5 grams, [380] those with 50-100 such organs 7 grams and those with a bright crown 10 grams, the appendices being removed before the weighing. Corresponding results have been reached by the comparison of the height of the capsules with their abnormal surroundings. The degree of development of the monstrosity is shown by this observation to be directly dependent on, and in a sense proportionate to the individual strength of the plant.

The differences between the specimens grown from a single lot of seeds, for instance from the seeds of one self-fertilized capsule are, as I have said, partly due to the divergences which are always present in a bed, even if the utmost care has been taken to make it as uniform as possible. These local differences are ordinarily underrated and overlooked, and it is often considered to be sufficient to cultivate small lots of plants under apparently similar conditions on neighboring beds, to be justified in imputing all the observed deviations of the plants to hereditary inequalities. This of course is true for large lots, whenever the averages only are compared. In smaller experiments the external conditions of the single individuals should always be considered carefully. Lots of one or two square meters suffice for such comparisons, but smaller lots are always subject to chances and [381] possibilities, which should never be left out of consideration.

Therefore I will now point out some circumstances, which are ordinarily different on various parts of one and the same bed.

In the first place comes the inequality of the seeds themselves. Some of them will germinate earlier and others later. Those that display their cotyledons on a sunny day will be able to begin at once with the production of organic food. Others appear in bad weather, and will thus be retarded in their development. These effects are of a cumulative nature as the young plants must profit by every hour of sunshine, according to the size of the cotyledons. Any inequality between two young seedlings is apt to be increased by this cumulative effect.

The same holds good for the soil of the bed. It is simply impossible to mix the manure so equally that all individuals receive the same amount of it from the very beginning. I am in the habit of using manures in a dry and pulverized condition, of giving definite quantities to each square meter, and of taking the utmost care to get equal distribution and mixture with the soil, always being present myself during this most important operation. Nevertheless it is impossible to make the nourishment exactly equal for all the plants of even a small bed.

[382] Any inequality from this cause will increase the difference in the size of the young leaves, augment the inequality of their production of organic matter and for this reason go on in an ever increasing rate.

Rain and spraying, or on the other hand dryness of the soil, have still greater consequences. The slightest unevenness of the surface will cause some spots to dry rapidly and others to retain moisture during hours and even sometimes during days.

Seeds, germinating in such little moist depressions grow regularly and rapidly, while those on the dryer elevations may be retarded for hours and days, before fully unfurling their seed-leaves. After heavy rains these differences may be observed to increase continually, and in some instances I found that plants were produced only on the wet spots, while the dry places remained perfectly bare. From this the wet spots seem to be the most favorable, but on the other hand, seeds may come to germinate there too numerously and so closely that the young plants will be crowded together and find neither space nor light enough, for a free and perfect development. The advantage may change to disadvantage in this way unless the superfluous individuals are weeded out in due time.

[383] From all these and other reasons some plants will be favored by the external conditions from the beginning, while others will be retarded, and the effects will gradually increase until at last they become sufficient to account for a considerable amount of individual variability. There is no doubt that the difference in the strength of the plant and in the size of the capsules, going from 5-10 grams for a single fruit, are for the most part due to these unavoidable circumstances. I have tried all conceivable means to find remedies for these difficulties, but only by sowing my seeds in pans in a glass-house have I been able to reach more constant and equal conditions. But unfortunately such a method requires the planting out of the young seedlings in the beginning of the summer, and this operation is not without danger for opium-poppies, and especially not without important influence on the monstrosity of the pistilloid variety. Consequently my sowings of this plant have nearly always been made in the beds.

In order to show how great the influence of all these little things may become, we only have to make two sowings on neighboring beds and under conditions which have carefully been made as equal as possible. If we use for these controlling experiments seeds from one and the same capsule, it will soon become evident that [384] no exact similarity between the two lots may be expected. Such differences as may be seen in these cases are therefore never to be considered of value when comparing two lots of seeds of different origin, or under varying conditions. No amount of accuracy in the estimation of the results of a trial, or in the counting out of the several degrees of the anomaly, is adequate to overcome the inaccuracy resulting from these differences.

It is certainly of great importance to have a correct conception in regard to the influence of the surrounding conditions on the growth of a plant and on the development of the attribute we are to deal with. No less important is the question of the sensibility of the plants to these factors. Obviously this sensibility must not be expected to remain the same during the entire life-period, and periods of stronger and of weaker responses may be discerned.

In the first place it is evident that external or inner influences are able to change the direction of the development of an organ only so long as this development is not yet fully finished. In the young flower-bud of the pistilloid poppy there must evidently be some moment in which it is definitely decided whether the young stamens will grow out normally or become metamorphosed into secondary pistils. From this [385] moment no further change of external conditions is able to produce a corresponding change in the degree of the anomaly. The individual strength of the whole plant may still be affected in a more or less manifest degree, but the number of converted stamens of the flower has been definitely fixed. The sensitive period has terminated.

In order to determine the exact moment of this termination of the period of sensibility, I have followed the development of the flower buds during the first weeks of the life of the young plants. The terminal flower may already be seen in young plants only seven weeks old, with a stem not exceeding 5-6 cm. in height and a flower-bud with a diameter of nearly 1 mm., in which the stamens and secondary pistils are already discernible, but still in the condition of small rounded protuberances on the thalamus. Though it is not possible at that time to observe any difference between the future normal and converted stamens, it does not seem doubtful that the development is so far advanced, that in the inner tissues the decision has already definitely been taken. In the next few days this decision rapidly becomes visible, and the different parts of the normal stamens and the metamorphosed carpels soon become apparent. From this observation it [386] can be inferred that the sensitive period of the anomaly is limited for the terminal flower-head, to the first few weeks of the life of the young plants. The secondary heads manifestly leave this period at a somewhat later stage.

In order to prove the accuracy of this conclusion I have tried to injure the anomalies after the expiration of the first six or seven weeks. I deprived them of their leaves, and damaged them in different ways. I succeeded in making them very weak and slender, without being able to diminish the number of the supernumerary carpels. The proportionality of the size of the central fruit and the development of the surrounding crown can often be modified or even destroyed by this means, and the apparent exceptions from this rule, which are often observed, may find their explanation in this way.

In the second place I have tried to change the development of the anomaly during the period of sensibility, and even in the last part of it. This experiment succeeded fully when carried out within the fifth or sixth week after the beginning of the germination. As means of injury I transplanted the young plants. To this end I sowed my seeds in pans in unmanured soil, planted them out in little pots with richly prepared earth, grew them in these during a few weeks and afterwards transferred them to the [387] beds, taking care that the pats were removed, but the balls of earth not broken.

In consequence of this treatment the plants became very large and strong, with luxuriant foliage and relatively numerous large flowers and fruits. But almost without exception they were poor in anomalous stamens, at least so on the terminal heads. On a lot of some 70 plants more than 50 had less than half a crown of secondary capsules, while from the same packet of seed the control-plants gave in an equal number more than half of filled crowns on all plants with the exception of five weak specimens.

It is curious to compare such artificially injured plants with the ordinary cultures. Strong stems and heavy fruits, which otherwise are always indicative of showy crowns, now bear fruits wholly or nearly destitute of any anomalous change. The commonly prevailing rule seems to be reversed, showing thereby the possibility of abolishing the correlation between individual strength and anomaly by an artificial encroachment upon the normal conditions.

Aside from these considerations the experiments clearly give proof of the existence of a period of sensibility limited to the first weeks of the life of the plant for the terminal flower. This knowledge enables us to explain many apparent [388] parent abnormalities, which may occur in the experiments.

We now may take a broader view of the period of sensibility. Evidently the response to external influences will be greater the younger the organ. Sensibility will gradually diminish, and the phenomena observed in the last part of this period may be considered as the last remainder of a reaction which previously must have been much stronger and much readier, providing that it would be possible to isolate them from, and contrast them with, the other responses of the same plant.

With the light thus cast upon the question, we may conclude that the sensitive period commences not only at the beginning of the germination, but must also be considered to include the life of the seed itself. From the moment of fertilization and the formation of the young embryo the development must be subjected to the influence of external agencies which determine the direction it will take and the degree of development it will finally be able to acquire. Probably the time of growth of the embryo and of the ripening of the seed correspond exactly to the period of highest sensibility. This period is only interrupted during the resting stage of the seed, to be repeated in germination. Afterwards the sensibility [389] slowly and gradually decreases, to end with the definite decision of all further growth sometime before the outer form of the organ becomes visible under the microscope. The last period of life includes only an expansion of the tissues, which may still have some influence on their final size, but not on their form. This has been definitely arrested before the end of the sensitive period, and ordinarily before the commencement of that rapid development, which is usually designated by the name of growth, as contrasted with evolution.

Within the seed the evolution of the young plant manifestly depends upon the qualities and life-conditions of the parent-plant. The stronger this is, and the more favorable circumstances it is placed under, the more food will be available for the seed, and the healthier will be the development of the embryo. Only well-nourished plants give well-nourished seeds, and the qualities of each plant are for this reason at least, partly dependent on the properties of its parents and even of its grandparents.

From these considerations the inference is forced upon us that the apparently hereditary differences, which are observed to exist among the seeds of a species or a variety and even of a single strain or a single parent-plant, may for a large part, and perhaps wholly, be the result [390] of the life-conditions of their parents and grandparents. Within the race all ssvariability would in this way be reduced to the effects of external circumstances. Among these nourishment is no doubt the most momentous, and this to such a degree that older writers designated the external conditions by the term nourishment. According to Knight nutrition reigns supreme in the whole realm of variability, the kind of food and the method of nourishment coming into consideration only in a secondary way. The amount of useful nutrition is the all-important factor.

If this is so, and if nutrition decides the degree of deviation of any given character, the widest deviating individuals are the best nourished ones. The best nourished not only during the period of sensibility of the attribute under consideration, but also in the broadest sense of the word.

This discussion casts a curious light upon the whole question of selection. Not of course upon the choice of elementary species or varieties out of the original motley assembly which nature and old cultures offer us, but upon the selection of the best individuals for isolation and for the improvement of the race. These are, according to my views, only the best nourished ones. Their external conditions have been the [391] most favorable, not only from the beginning of their own life in the field, but also during their embryonic stages, and even during the preparation of these latter in the life of their parents and perhaps even their grandparents. Selection then, would only be the choice of the best nourished individuals.

In connection with the foregoing arguments I have tried to separate the choicest of the poppies with the largest crown of pistilloid stamens, from the most vigorous individuals. As we have already seen, these two attributes are as a rule proportional to one another. Exceptions occur, but they may be explained by some later changes in the external circumstances, as I have also pointed out. As a rule, these exceptions are large fruits with comparatively too few converted stamens; they are exactly the contrary from what is required for a selection. Or plants, which from the beginning were robust, may have become crowded together by further growth, and for these reasons become weaker than their congeners, though retaining the full development of the staminodal crown, which was fixed during the sensitive period and before the crowding. I have searched my beds yearly for several years in vain to find individuals which might recommend themselves for selection without having the stamp of permanent, [392] or at least temporarily better, nourishment. No starting-point for such an independent selection has ever been met with.

Summing up the consequences of this somewhat extended discussion, we may state it as a rule that a general proportion between the individual strength and the degree of development of the anomaly exists. And from this point of view it is easy to see that all external causes which are known to affect the one, must be expected to influence the other also.

It will therefore hardly be necessary to give a full description of all my experiments on the relations of the monstrosity to external conditions. A hasty survey will suffice.

This survey is not only intended to convey an idea of the relations of pistilloid poppies to their environment, but may serve as an example of the principle involved. According to my experience with a large range of other anomalies, the same rule prevails everywhere. And this rule is so simple that exact knowledge of one instance may be considered as sufficient to enable us to calculate from analogy what is to be expected from a given treatment of any other anomaly. Our appreciation of observed facts and the conditions to be chosen for intended cultures are largely dependent on such calculations. What I am now going to describe [393] is to be considered therefore as an experimental basis for such expectations.

First of all comes the question how many individuals are to be grown in a given place. When sowing plants for experimental purposes it is always best to sow in rows, and to give as few seeds to each row as possible, so as to insure all necessary space to the young plants. On the other hand the seeds do not all germinate, and after sowing too thinly, gaps may appear in the rows. This would cause not only a loss of space, but an inequality between the plants in later life, as those nearest the gaps would have more space and more light, and a larger area for their roots than those growing in the unbroken rows. Hence the necessity of using large quantities of seed and of weeding out a majority of young plants on the spots where the greatest numbers germinate.

Crowded cultures as a rule, will give weak plants with thin stems, mostly unbranched and bearing only small capsules. According to the rule, these will produce imperfect crowns of secondary pistils. The result of any culture will thus be dependent to a high degree on the number of individuals per square meter. I have sown two similar and neighboring beds with the thoroughly mixed seeds of parent-plants of the same strain and culture, using as much [394] as 2.5 cu. cm. per square meter. On one of the beds I left all the germinating plants untouched and nearly 500 of them flowered, but among them 360 were almost without pistillody, and only 10 had full crowns. In the other bed I weeded away more than half of the young plants, leaving only some 150 individuals and got 32 with a full crown, nearly 100 with half crowns and only 25 apparently without monstrosity.

These figures are very striking. From the same quantity of seed, in equal spaces, by similar exposure and treatment I got 10 fully developed instances in one and 32 in the other case. The weeding out of supernumerary individuals had not only increased the percentage of bright crowns, but also their absolute number per square meter. So the greatest number of anomalies upon a given space may be obtained by taking care that not too many plants are grown upon it: any increase of the number beyond a certain limit will diminish the probability of obtaining these structures. The most successful cultures may be made after the maximum number of individuals per unit of area has been determined. A control-experiment was made under the same conditions and with the same seed, but allowing much less for the same space. I sowed only 1 cu. cm. on my bed of 2 square meters, and thereby avoided [395] nearly all weeding out. I got 120 plants, and among them 30 with full crowns of converted stamens, practically the same number as after the weeding out in the first experiment. This shows that smaller quantities of seed give an equal chance for a greater number of large crowns, and should therefore always be preferred, as it saves both seed and labor.

Weeding out is a somewhat dangerous operation in a comparative trial. Any one who has done it often, knows that there is a strong propensity to root out the weaker plants and to spare the stronger ones. Obviously this is the best way for ordinary purposes, but for comparisons evidently one should not discriminate. This rule is very difficult in practice, and for this reason one should never sow more than is absolutely required to meet all requirements.

Our second point is the manuring of the soil. This is always of the highest importance, both for normal and for anomalous attributes. The conversion of the stamens into pistils is in a large measure dependent upon the conditions of the soil. I made a trial with some 800 flowering plants, using one sample of seed, but sowing one-third on richly manured soil, one-third on an unprepared bed of my garden, and one-third on nearly pure sand. In all other respects the three groups were treated in the same way. Of [396] the manured plants one-half gave full crowns, of the non-manured only one-fifth, and on the sandy soil a still smaller proportion. Other trials led to the same results. I have often made use of steamed and ground horn, which is a manure very rich in nitrogenous substances. One-eighth of a kilo per square meter is an ample amount. And its effect was to increase the number of full crowns to an exceptional degree.

In the controlling trial and under ordinary circumstances this figure reached some 50%, but with ground horn it came up as high as 90%. We may state this result by the very striking assertion that the number of large crowns in a given culture may be nearly doubled by rich manure.

All other external conditions act in a similar manner. The best treatment is required to attain the best result. A sunny exposure is one of the most essential requisites, and in some attempts to cultivate my poppies in the shade, I found the pistillody strongly reduced, not a single full crown being found in the whole lot. Often the weather may be hurtful, especially during the earlier stages of the plants. I protected my beds during several trials by covering them with glass for a few weeks, until the young plants reached the glass covering. I got a normal number of full crowns, some 55%, at a time [397] when the weather was so bad as to reduce the number in the control experiments to 10%.

It would be quite superfluous to give more details or to describe additional experiments. Suffice to say, that the results all point in the same direction, and that pistillody of the poppies always clearly responds to the treatment, especially to external conditions during the first few weeks, that is, during the period of sensitiveness. The healthier and the stronger the plants the more fully they will develop their anomaly.

In conclusion something is to be said about the choice of the seed. Obviously it is possible to compare seeds of different origin by sowing and treating them in the same way, giving attention to all the points above mentioned. In doing so the first question will be, whether there is a difference between the seeds of strong plants with a bright crown around the head and those of weaker individuals with lesser development of the anomaly. It is evident that such a difference must be expected, since the nutrition of the seed takes place during the period of the greatest sensitiveness.

But the experiments will show whether this effect holds good against the influences which tend to change the direction of the development of the anomaly during the time of germination. [398] The result of my attempt has shown that the choice of the seeds has a manifest influence upon the ultimate development of the monstrosity, but that this influence is not strong enough to overwhelm all other factors.

The choice of the fullest or smallest crowns may be repeated during succeeding generations, and each time compared with a culture under average conditions. By this means we come to true selection-experiments, and these result in a notable and rapid change of the whole strain. By selecting the brightest crowns I have come up in three years from 40 to 90 and ultimately to 120 converted stamens in the best flower of my culture, and in selecting the smallest crowns I was able in three years to exclude nearly all good crowns, and to make cultures in which heads with less than half-filled crowns constituted the majority. But such selected strains always remain very sensitive to treatment, and by changing the conditions the effect may be wholly lost in a single year, or even turned in the contrary direction. In other words, the anomaly is more dependent on external conditions during the germinating period than on the choice of the seeds, providing these belong to the pistilloid variety and have not deteriorated by some crossing with other sorts.

At the beginning of this lecture I stated that [399] no selection is adequate to produce either a pure strain of brightly crowned flower-heads without atavism, or to conduce to an absolute and permanent loss of the anomaly. During a series of years I have tested my plants in both directions, but without the least effect. Limits are soon reached on both sides, and to transgress these seems quite impossible.

Taking these limits as the marks of the variety, and considering all fluctuations between them as responses to external influences working during the life of the individual or governing the ripening of the seeds, we get a clear picture of a permanent ever-sporting type. The limits are absolutely permanent during the whole existence of this already old variety. They never change. But they include so wide a range of variability, that the extremes may be said to sport into one another, so much the more so as one of the extremes is to be considered morphologically as the type of the variation, while the other extreme can hardly be distinguished from the normal form of the species.



[400]

LECTURE XIV

MONSTROSITIES

I have previously dealt with the question of the hereditary tendencies that cause monstrosities. These tendencies are not always identical for the same anomaly. Two different types may generally, be distinguished. One of them constitutes a poor variety, the other a rich one. But this latter is abundant and the first one is poor in instances of exactly the same conformation. Therefore the difference only lies in the frequency of the anomaly, and not in its visible features. In discovering an instance of any anomaly it is therefore impossible to tell whether it belongs to a poor or to a rich race. This important question can only be answered by direct sowing-experiments to determine the degree of heredity.

Monstrosities are often considered as accidents, and rightfully so, at least as long as they are considered from a morphological point of view. Physiology of course excludes all accidentality. And in our present ease it shows [401] that some internal hereditary quality is present, though often latent, and that the observed anomalies are to be regarded as responses of this innate tendency to external conditions. Our two types differ in the frequency of these responses. Rare in the poor race, they are numerous in the rich variety. The external conditions being the same for both, the hereditary factor must be different. The tendency is weak in the one and strong in the other. In both cases, according to my experience, it may be weakened or strengthened by selection and by treatment. Often to a very remarkable degree, but not so far as to transgress the limits between the two races. Such transgression may apparently be met with from time to time, but then the next generation generally shows the fallacy of the conclusion, as it returns more or less directly to the type from which the strain had been derived. Monstrosities should always be studied by physiologists from this point of view. Poor and rich strains of the same anomaly seem at first sight to be so nearly allied that it might be thought to be very easy to change the one into the other. Nevertheless such changes are not on record, and although I have made several attempts in this line, I never succeeded in passing the limit. I am quite convinced that sometime [402] a method will be discovered of arbitrarily producing such conversions, and perhaps the easiest way to attain artificial mutations may lie concealed here. But as yet not the slightest indication of this possibility is to be found, save the fallacious conclusions drawn from too superficial observations.

Unfortunately the poor strains are not very interesting. Their chance of producing beautiful instances of the anomaly for which they are cultivated is too small. Exceptions to this rule are only afforded by those curious and rare anomalies, which command general attention, and of which, therefore, instances are always welcome. In such cases they are searched for with perseverance, and the fact of their rarity impresses itself strongly on our mind.

Twisted stems are selected as a first example. This monstrosity, called biastrepsis, consists of strongly marked torsions as are seen in many species with decussate leaves, though as a rule it is very rare. Two instances are the most generally known, those of the wild valerian (Valeriana officinalis) and those of cultivated and wild sorts of teasels (Dipsacus fullonum, D. sylvestris, and others). Both of these I have cultivated during upwards of fifteen years, but with contradictory results. The valerian is a perennial herb, multiplying itself yearly by [403] slender rootstocks or runners producing at their tips new rosettes of leaves and in the center of these the flowering stem. My original plant has since been propagated in this manner, and during several years I preserved large beds with hundreds of stems, in others I was compelled to keep my culture within more restricted limits. This plant has produced twisted stems of the curious shape, with a nearly straight flag of leaves on one side, described by De Candolle and other observers, nearly every year. But only one or two instances of abnormal stems occurred in each year, and no treatment has been found that proved adequate to increase this number in any appreciable manner. I have sown the seeds of this plant repeatedly, either from normal or from twisted stems, but without better results. It was highly desirable to be able to offer instances of this rare and interesting peculiarity to other universities and museums, but no improvement of the race could be reached and I have been constrained to give it up. My twisted valerian is a poor race, and hardly anything can be done with it. Perhaps, in other countries the corresponding rich race may be hidden somewhere, but I have never had the good fortune of finding it.

This good fortune however, I did have with the wild teasel or Dipsacus sylvestris. [404] Stems of this and of allied species are often met with and have been described by several writers, but they were always considered as accidents and nobody had ever tried to cultivate them. In the summer of 1885 I saw among a lot of normal wild teasels, two nicely twisted stems in the botanical garden of Amsterdam. I at once proposed to ascertain whether they would yield a hereditary race and had all the normal individuals thrown away before the flowering time. My two plants flowered in this isolated condition and were richly pollinated by insects. Of course, at that time, I knew nothing of the dependency of monstrosities on external conditions, and made the mistake of sowing the seeds and cultivating the next generation in too great numbers on a small space. But nevertheless the anomaly was repeated, and the aberrant individuals were once more isolated before flowering. The third generation repeated the second, but produced sixty twisted stems on some 1,600 individuals. The result was very striking and quite sufficient for all further researches, but the normal condition of the race was not reached. This was the case only after I had discovered the bad effects of growing too many plants in a limited space. In the fourth generation I restricted my whole culture to about 100 individuals, and by this simple [405] means at once got up to 34% of twisted stems. This proportion has since remained practically the same. I have selected and isolated my plants during five succeeding generations, but without any further result, the percentage of twisted stems fluctuating between 30 and about 45 according to the size of the cultures and the favorableness or unfavorableness of the weather.

It is very interesting to note that all depends on the question whether one has the good fortune of finding a rich race or not, as this pedigree-culture shows. Afterwards everything depends on treatment and very little on selection. As soon as the treatment becomes adequate, the full strength of the race at once displays itself, but afterwards no selection is able to improve it to any appreciable amount. Of course, in the long run, the responses will be the same as those of the pistilloid poppies on the average, and some influence of selection will show itself on closer scrutiny.

Compared with the polycephalous poppies my race of twisted teasels is much richer in atavists. They are never absent, and always constitute a large part of each generation and each bed, comprising somewhat more than half of the individuals. Intermediate stages between them and the wholly twisted stems are not wanting, [406] and a whole series of steps may easily be observed from sufficiently large cultures. But they are always relatively rare, and any lot of plants conveys the idea of a dimorphous race, the small twisted stems contrasting strongly with the tall straight ones.

A sharper contrast between good representatives of a race and their atavists is perhaps to be seen in no other instance. All the details contribute to the differentiation in appearance. The whole stature of the plants is affected by the varietal mark. The atavists are not, as in the case of the poppies, obviously allied with the type by a full range of intermediate steps, but quite distant from it by their rarity. There seems to be a gap in the same way as between the striped flowers of the snapdragon and their uniform red atavists, while with the poppies the atavists may be viewed as being only the extremes of a series of variations fluctuating around some average type.

From this reason it is as interesting to appreciate the hereditary position of the atavists of twisted varieties as it was for the red-flowered descendants of the striped flowers. In order to ascertain this relation it is only necessary to isolate some of them during the blooming-period. I made this experiment in the summer of 1900 with the eighth generation of my race, and contrived [407] to isolate three groups of plants by the use of parchment bags, covering them alternately, so the flowers of only one group were accessible to insects, at a time. I made three groups, because the atavists show two different types. Some specimens have decussate stems, others bear all their leaves in whorls of three, but in respect to the hereditary tendency of the twisting character this difference does not seem to be of any importance.

In this way I got three lots of seeds and sowed enough of them to have three groups of plants each containing about 150-200 well developed stems. Among these I counted the twisted individuals, and found nearly the same numbers for all three. The twisted parents gave as many as 41% twisted children, but the decussate atavists gave even somewhat more, viz., 44%, while the ternate specimens gave 37%. Obviously the divergences between these figures are too slight to be dwelt upon, but the fact that the atavists are as true or nearly as true inheritors of the twisted race as the best selected individuals is clearly proved by this experience.

It is evident that here we have a double race, including two types, which may be combined in different degrees. These combinations determine a wide range of changes in the stature of the plants, and it seems hardly right to use the [408] same term for such changes as for common variations. It is more a contention of opposite characters than a true phenomenon of simple variability. Or perhaps we might say that it is the effect of the cooperation of a very variable mark, the twisting, with a scarcely varying attribute of the normal structure of the stem. Between the two types an endless diversity prevails, but outwardly there are limits which are never transgressed. The double race is as permanent, and in this sense as constant, as any ordinary simple variety, both in external form, and in its intimate hereditary qualities.

I have succeeded in discovering some other rich races of twisted plants. One of them is the Sweet William (Dianthus barbatus), which yielded, after isolation, in the second generation, 25% of individuals with twisted stems, and as each individual produces often 10 and more stems, I had a harvest of more than half a thousand of instances of this curious, and ordinarily very rare anomaly. My other race is a twisted variety of Viscaria oculata, which is still in cultivation, as it has the very consistent quality of being an annual. It yielded last summer (1903) as high a percentage as 65 of twisted individuals, many of them repeating the monstrosity on several branches. After some occasional observations Gypsophila paniculata [409] seems to promise similar results. On the other hand I have sowed in vain the seeds of twisted specimens of the soapwort and the cleavewort (Saponaria officinalis and Galium Aparine). These and some others seem to belong to the same group as the valerian and to constitute only poor or so-called half-races.

Next to the torsions come the fasciated stems. This is one of the most common of all malformations, and consists, in its ordinary form, of a flat ribbon-like expansion of the stems or branches. Below they are cylindrical, but they gradually lose this form and assume a flattened condition. Sometimes the rate of growth is unequal on different portions or on the opposite sides of the ribbon, and curvatures are produced and these often give to the fasciation a form that might be compared with a shepherd's crook. It is a common thing for fasciated branches and stems to divide at the summit into a number of subdivisions, and ordinarily this splitting occurs in the lower part, sometimes dividing the entire fasciated portion. In biennial species the rosette of the root-leaves of the first year may become changed by the monstrosity, the heart stretching in a transverse direction so as to become linear. In the next year this line becomes the base from which the stem grows. In such cases the fasciated stems [410] are broadened and flattened from the very beginning, and often retain the incipient breadth throughout their further development. Species of primroses (Primula japonica and others), of buttercups (Ranunculus bulbosus), the rough hawksbeard (Crepis biennis), the Aster Tripolium, and many others could be given as instances.

Some of these are so rare as to be considered as poor races, and in cultural trials do not produce the anomaly except in a very few instances. Heads of rye are found in a cleft condition from time to time, single at their base and double at the top, but this anomaly is only exceptionally repeated from seed. Flattened stems of Rubia tinctorum are not unfrequently met with on the fields, but they seem to have as little hereditary tendency as the split rye (Secale Cereale). Many other instances could be given. Both in the native localities and in pedigree-cultures such ribboned stems are only seen from time to time, in successive years, in annual and biennial as well as in perennial species. The purple pedicularis (Pedicularis palustris) in the wild state, and the sunflower among cultivated plants, may be cited instead of giving a long list of analogous instances.

On the other hand rich races of flattened stems are not entirely lacking. They easily betray [411] themselves by the frequency of the anomaly, and therefore may be found, and tried in the garden. Under adequate cultivation they are here as rich in aberrant individuals as the twisted races quoted above, producing in good years from 30-40% and often more instances. I have cultivated such rich races of the dandelion (Taraxacum officinale), of Thrincia hirta, of the dame's violet (Hesperis matronalis), of the hawkweed (Picris hieracioides), of the rough hawksbeard (Crepis biennis), and others.

Respecting the hereditary tendencies these rich varieties with flattened stems may be put in the same category with the twisted races. Two points however, seem to be of especial interest and to deserve a separate treatment.

The common cockscomb or Celosia cristata, one of the oldest and most widely cultivated fasciated varieties may be used to illustrate the first point. In beds it is often to be seen in quite uniform lots of large and beautiful crests, but this uniformity is only secured by careful culture and selection of the best individuals. In experimental trials such selection must be avoided, and in doing so a wide range of variability at once shows itself. Tall, branched stems with fan-shaped tops arise, constituting a series of steps towards complete atavism. This last [412] however, is not to be reached easily. It often requires several successive generations grown from seed collected from the most atavistic specimens. And even such selected strains are always reverting to the crested type. There is no transgression, no springing over into a purely atavistic form, such as may be supposed to have once been the ancestor of the present cockscomb. The variety includes crests and atavists, and may be perpetuated from both. Obviously every gardener would select the seeds of the brightest crests, but with care the full crests may be recovered, even from the worst reversionists in two or three generations. It is a double race of quite the same constitution as the twisted teasels.

My second point is a direct proof of this assertion, but made with a fasciated variety of a wild species. I took for my experiment the rough hawksbeard. In the summer of 1895 I isolated some atavists of the fifth generation of my race, which, by ordinary selection, gave in the average from 20-40% of fasciated stems. My isolated atavists bore abundant fruit, and from these I had the next year a set of some 350 plants, out of which about 20% had broadened and linear rosettes. This proportion corresponds with the degree of inheritance which is shown in many years by the largest and strongest [413] fasciated stems. It strengthens our conclusion as to the innermost constitution of the double races or ever-sporting varieties.

Twisted stems and fasciations are very striking monstrosities. But they are not very good for further investigation. They require too much space and too much care. The calculation of a single percentage requires the counting of some hundreds of individuals, taking many square meters for their cultivation, and this, as my best races are biennial, during two years. For this reason the countings must always be very limited, and selection is restrained to the most perfect specimens.

Now the question arises, whether this mark is the best upon which to found selection. This seems to be quite doubtful. In the experiments on the heredity of the atavists, we have seen that they are, at least often, in no manner inferior to even the best inheritors of the race. This suggests the idea that it is not at all certain that the visible characters of a given individual are a trustworthy measure of its value as to the transmission of the same character to the offspring. In other words, we are confronted with the existence of two widely different groups of characters in estimating the hereditary tendency. One is the visible quality of the individuals and the other is the direct observation [414] of the degree in which the attribute is transmitted. These are by no means parallel, and seem in some sense to be nearly independent of each other. The fact that the worst atavists may have the highest percentage of varietal units seems to leave no room for another explanation.

Developing this line of thought, we gradually arrive at the conclusion that the visible attribute of a varying individual is perhaps the most untrustworthy and the most unreliable character for selection, even if it seems in many cases practically to be the only available one. The direct determination of the degree of heredity itself is obviously preferable by far. This degree is expressed by the proportion of its inheritors among the offspring, and this figure therefore should be elevated to the highest rank, as a measure of the hereditary qualities. Henceforward we will designate it by the name of hereditary percentage.

In scientific experiments this figure must be determined for every plant of a pedigree-culture singly, and the selection should be founded exclusively or at least mainly on it. It is easily seen that this method requires large numbers of individuals to be grown and counted. Some two or three hundred progeny of one plant are needed to give the decisive figure for this one [415] individual, and selection requires the comparison of at least fifty or more individuals. This brings the total amount of specimens to be counted up to some tens of thousands. In practice, where important interests depend upon the experiments, such numbers are usually employed and often exceeded, but for the culture of monstrosities, other methods are to be sought in order to avoid these difficulties.

The idea suggests itself here that the younger the plants are, when showing their distinguishing marks, the more of them may be grown on a small space. Hence the best way is to choose such attributes, as may already be seen in the young seedlings, in the very first few weeks of their lives. Fortunately the seed-leaves themselves afford such distinctive marks, and by this means the plants may be counted in the pans, requiring no culture at all in the garden. Only the selected individuals need be grown to ripen their seeds, and the whole selection may be made in the spring, in the glasshouse. Instead of being very troublesome, the determination of the hereditary percentages becomes a definite reduction of the size of the experiments. Moreover it may easily be effected by any one who cares for experimental studies, but has not the means required for cultures on a larger scale. And lastly, there are [416] a number of questions about heredity, periodicity, dependency on nourishment and other life conditions, and even about hybridizing, which may be answered by this new method.

Seed-leaves show many deviations from the ordinary shape, especially in dicotyledonous plants. A very common aberration is the multiplication of their number, and three seed-leaves in a whorl are not rarely met with. The whorl may even consist of four, and in rare cases of five or more cotyledons. Cleft cotyledons are also to be met with, and the fissure may extend varying distances from the tips. Often all these deviations may be seen among the seedlings of one lot, and then it is obvious that together they constitute a scale of cleavages, the ternate and quaternate whorls being only cases where the cleaving has reached its greatest development. All in all it is manifest that here we are met by one type of monstrosity, but that this type allows of a wide range of fluctuating variability. For brevity's sake all these cleft and ternate, double cleft and quaternate cotyledons and even the higher grades are combined under one common name and indicated as tricotyls.

A second aberration of young seed-plants is exactly opposite to this. It consists of the union of the two seed-leaves into a single organ. This ordinarily betrays its origin by [417] having two separate apices, but not always. Such seedlings are called syncotyledonous or syncotyls. Other monstrosities have been observed from time to time, but need not be mentioned here.

It is evident that the determination of the hereditary percentage is very easy in tricotylous or syncotylous cultures. The parent plants must be carefully isolated while blooming. Many species pollinate themselves in the absence of bees; from these the insects are to be excluded. Others have the stamens and stigmas widely separated and have to be pollinated artificially. Still others do not lend themselves to such operations, but have to be left free to the visits of bees and of humble-bees, this being the only means of securing seed from every plant. At the time of the harvest the seeds should be gathered separately from each plant, and this precaution should also be observed in studies of the hereditary percentage at large, and in all scientific pedigree-cultures. Every lot of seeds is to be sown in a separate pan, and care must be taken to sow such quantities the three to four hundred seedlings will arise from each. As soon as they display their cotyledons, they are counted, and the number is the criterion of the parent-plant. Only parent-plants with the highest percentages are selected, and out of [418] their seedlings some fifty or a hundred of the best ones are chosen to furnish the seeds for the next generation.

This description of the method shows that the selection is a double one. The first feature is the hereditary percentage. But then not all the seedlings of the selected parents can be planted out, and a choice has to be made. This second selection may favor the finest tricotyls, or the strongest individuals, or rely on some other character, but is unavoidable.

We now come to the description of the cultures. Starting points are the stray tricotyls which are occasionally found in ordinary sowings. In order to increase the chance of finding them, thousands of seeds of the same species must be inspected, and the range of species must be widened as much as possible.

Material for beginning such experiments is easily obtained, and almost any large sample of seeds will be found suitable. Some tricotyls will be found among every thousand seedlings in many species, while in others ten or a hundred times, as many plants must be examined to secure them, but species with absolutely pure dicotylous seeds are very rare.

The second phase of the experiment, however, is not so promising. Some species are rich, and others are poor in this anomaly. This difference [419] often indicates what can be expected from further culture. Stray tricotyls point to poor species or half-races, while more frequent deviations suggest rich or double-races. In both cases however, the trial must be made, and this requires the isolation of the aberrant individuals and the determination of their hereditary percentage.

In some instances the degree of their inheritance is only a very small one. The isolated tricotyls yield 1 or 2% of inheritors, in some cases even less, or upwards up to 3 or 4%. If the experiment is repeated, no amelioration is observed, and this result remains the same during a series of successive generations. In the case of Polygonum convolvulus, the Black bindweed, I have tried as many as six generations without ever obtaining more than 3%. With other species I have limited myself to four successive years with the same negative result, as with spinage, the Moldavian dragon-head, (Dracocephalum moldavicum), and two species of corn catch-fly (Silene conica and S. conoidea).

Such poor races hardly afford a desirable material for further inquiries. Happily the rich races, though rare, may be discovered also from time to time. They seem to be more common among cultivated plants and horticultural as well as agricultural species may be used. Hemp [420] and mercury (Mercurialis annua) among the first, snapdragon, poppies, Phacelia, Helichrysum, and Clarkia among garden-flowers may be given as instances of species containing the rich tricotylous double races.

It is very interesting to note how strong the difference is between such cases and those which only yield poor races. The rich type at once betrays itself. No repeated selection is required. The stray tricotyls themselves, that are sought out from among the original samples, give hereditary percentages of a much higher type after isolation than those quoted above. They come up to 10-20% and in some cases even to 40%. As may be expected, individual differences occur, and it must even be supposed that some of the original tricotyls may not be pure, but hybrids between tricotylous and dicotylous parents. These are at once eliminated by selection, and if only the tricotyls which have the highest percentages are chosen for the continuance of the new race, the second generation comes up with equal numbers of dicotyls and tricotyls among the seedlings. The figures have been observed to range from 51-58% in the majority of the cases, and average 55%, rarely diverging somewhat more from this average.

Here we have the true type of an ever-sporting variety. Every year it produces in the [421] same way heirs and atavists. Every plant, if fertilized with its own pollen, gives rise to both types. The parent itself may be tricotylous or dicotylous, or show any amount of multiplication and cleavage in its seed-leaves, but it always gives the entire range among its progeny of the variation. One may even select the atavists, pollinate them purely and repeat this in a succeeding generation without any chance of changing the result. On an average the atavists may give lower hereditary figures, but the difference will be only slight.

Such tricotylous double races offer highly interesting material for inquiries into questions of heredity, as they have such a wide range of variability. There is little danger in asserting that they go upwards to nearly 100%, and downwards to 0%, diverging symmetrically on both sides of their average (50-55%). These limits they obviously cannot transgress, and are not even able to reach them. Samples of seed consisting only of tricotyls are very rare, and when they are met with the presumption is that they are too few to betray the rare aberrants they might otherwise contain. Experimental evidence can only be reached by the culture of a succeeding generation, and this always discloses the hidden qualities, showing that the double [422] type was only temporarily lost, but bound to return as soon as new trials are made.

This wide range of variability between definite limits is coupled with a high degree of sensibility and adequateness to the most diverging experiments. Our tricotylous double races are perhaps more sensitive to selection than any other variety, and equally dependent on outer circumstances. Here, however, I will limit myself to a discussion of the former point.

In the second generation after the isolation of stray tricotylous seedlings the average condition of the race is usually reached, but only by some of the strongest individuals, and if we continue the race, sowing or planting only from their offspring, the next generation will show the ordinary type of variability, going upwards in some and downwards in other instances. With the Phacelia and the mercury and some others I had the good luck in this one generation to reach as high as nearly 90% of tricotylous seedlings, a figure indicating that the normal dicotylous type had already become rare in the race. In other cases 80% or nearly 80% was easily attained. Any further divergence from the average would have required very much larger sowings, the effect of selection between a limited number of parents being only to retain the high degree once [423] reached; so for instance with the mercury, I had three succeeding generations of selection after reaching the average of 55%, but their extremes gave no increasing advance, remaining at 86, 92 and 91%.

If we compare these results with the effects of selection in twisted and fasciated races, we observe a marked contrast. Here they reached their height at 30-40%, and no number of generations had the power of making any further improvement. The tricotyls come up in two generations to a proportion of about 54%, which shows itself to correspond to the average type. And as soon as this is reached, only one generation is required to obtain a very considerable improvement, going up to 80 or even 90%.

It is evident that the cause of this difference does not lie in the nature of the monstrosity, but is due to the criterion upon which the selection is made. Selection of the apparently best individuals is one method, and it gives admirable results. Selection on the ground of the hereditary percentages is another method and gives results which are far more advantageous than the former.

In the lecture on the pistillody of the poppies we limited ourselves to the selection of the finest individuals and showed that there is always a manifest correlation between the individual [424] strength of the plant and the degree of development of its anomaly. The same holds good with other monstrosities, and badly nourished specimens of rich races with twisted or fasciated stems always tend to reversion. This reversion, however, is not necessarily correlated with the hereditary percentage and therefore does not always indicate a lessening of the degree of inheritance. This shows that even in those cases an improvement may be expected, if only the means can be found to subject the twisted and the fasciated races to the same sharp test as the tricotylous varieties.

Much remains to be done, and the principle of the selection of parents according to the average constitution of their progeny seems to be one of the most promising in the whole realm of variability.

Besides tricotylous, the syncotylous seedlings may be used in the same way. They are more rarely met with, and in most instances seem to belong only to the unpromising half-races. The black bindweed (Polygonum Convolvulus), the jointed charlock (Raphanus Raphanistrum), the glaucous evening-primrose (Oenothera glauca) and many other plants seem to contain such half-races. On the other hand I found a plant of Centranthus macrosiphon yielding as much as 55% of syncotylous children [425] and thereby evidently betraying the nature of a rich or double race. Likewise the mercury was rich in such deviations. But the best of all was the Russian sunflower, and this was chosen for closer experiments.