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]