By this method I brought my strain within two years up to an average of
nearly 90% of the seedlings with a divided primary leaf. Around this
average the real numbers fluctuated between the maximum of 99% and the
minimum of 70% or thereabouts. This condition was reached by the sixth
generation in the year 1894, and has since proved to be the limit, the
group of figures remaining practically the same during all the
succeeding generations.
Such selected plants are very rich in leaves with four, five and six
blades. Excluding the small leaves at the tops of the branches, and
those on the numerous weaker side-branches, these three groups include
the large majority of all the stronger leaves. In summer the range is
wider, and besides many trifoliolate leaves the curiously shaped
seven-bladed ones are not at all rare. In the fall and in the winter the
range of variability is narrowed, and at first sight the plants often
seem to bear only quinquefoliolate leaves.
[350] I have cultivated a new generation of this race nearly every year
since 1894, using always the strictest selection. This has led to a
uniform type, but has not been adequate to produce any further
improvement. Obviously the extreme limit, under the conditions of
climate and soil, has been reached. This extreme type is always
dependent upon repeated selection. No constant variety, in the older
sense, has been obtained, nor was any indication afforded that such a
type might ever be produced. On the contrary, it is manifest that the
new form belongs to the group of ever-sporting varieties. It is never
quite free from the old atavistic type of the trifoliolate leaves, and
invariably, when external conditions become less favorable, this
atavistic form is apt to gain dominion over the more refined varietal
character. Reversions always occur, both partial and individual.
Some instances of these reversions may now be given. They are not of
such a striking character as those of the snapdragon. Intermediate steps
are always occurring, both in the leaves themselves, and in the
percentages of deviating seedlings of the several parent plants.
On normal plants of my variety the quinquefoliolate leaves usually
compose the majority, when there are no weak lateral branches, or when
they are left out of consideration. Next [351] to these come the fours
and the sixes, while the trifoliolate and seven-bladed types are nearly
equal in number. But out of a lot of plants, grown from seed of the same
parent, it is often possible to choose some in which one extreme
prevails, and others with a preponderating number of leaves with the
other extreme number of leaflets. If seed from these extremes are saved
separately, one strain, that with numerous seven-bladed leaves will
remain true to the type, but the other will diverge more or less,
producing leaves with a varying number of subdivisions.
Public-domain text, read in full here on John Shaqi.
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