This seedling in the various species of clover usually begins with a
first leaf above the cotyledons of a different structure from those that
follow. It has only one blade instead of three. But in my variety the
increase of the number of the leaflets may extend to these primary
organs, and make them binate or even ternate. Now it is obvious that an
individual, which begins with a divided primary leaf, will have a
greater tendency to produce a large number of supernumerary leaflets
than a plant which commences in the ordinary way. Or in other words, the
primary leaves afford a sure criterion for the selection, and this
selection may be made in the seed-pans. In consequence, no young
individual with an undivided primary leaf was planted out. Choosing the
20 or 30 best specimens in the seed-pan, no further selection was
required, and the whole lot could be left to cross-fertilization by
insects.
The observation of this distinguishing mark in the young seedlings has
led to the discovery of another quality as a starting-paint for further
[348] selection. According to the general rule of pedigree-culture, the
seeds of each individual plant are always saved and sowed separately.
This is done even with such species as the clover, which are infertile
when self-pollinated, and which are incapable of artificial pollination
on the required scale, since each flower produces only one seed. My
clover was always left free to be pollinated by insects. Obviously this
must have led to a diminution of the differentiating characters of the
individual plants. But this does not go far enough to obliterate the
differences, and the selection made among the seedlings will always
throw out at least a large part of those that have suffered from the
cross.
Leaving this discussion, we may inquire closer into the nature of the
new criterion afforded by the seedlings. Two methods present themselves.
First, the choice of the best seedlings. In the second place it becomes
possible to compare the parent-plants by counting the number of
deviating seedlings. This leads to the establishment of a percentage for
every single parent, and gives data for comparisons. Two or three
hundreds of seeds from a parent may easily be grown in one pan, and in
this way a sufficiently high degree of accuracy may be reached. Only
those parents that give [349] the highest percentage are chosen, and
among their progeny only the seedlings with trifoliolate primary leaves
are planted out. The whole procedure of the selection is by this means
confined to the glasshouse during the spring, and the beds need not be
large, nor do they require any special care during the summer.
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