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.
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