The offspring
from the short-styled forms of dimorphic plants, and from both the mid-styled
and short-styled forms of trimorphic plants, fertilised with their own-form
pollen, likewise tend to belong to the same form as their parents, but not in so
marked a manner as in the case of the long-styled form. There are three cases in
Table 6.37, in which a form of Lythrum was fertilised illegitimately with pollen
from another form; and in two of these cases all the offspring belonged to the
same two forms as their parents, whilst in the third case they belonged to all
three forms.
The cases hitherto given relate to illegitimate unions, but Hildebrand, Fritz
Muller, and myself found that a very large proportion, or all of the offspring,
from a legitimate union between any two forms of the trimorphic species of
Oxalis belonged to the same two forms. A similar rule therefore holds good with
unions which are fully fertile, as with those of an illegitimate nature which
are more or less sterile. When some of the seedlings from a heterostyled plant
belong to a different form from that of its parents, Hildebrand accounts for the
fact by reversion. For instance, the long-styled parent-plant of Primula veris,
from which the 162 illegitimate seedlings in Table 6.36 were derived in the
course of five generations, was itself no doubt derived from the union of a
long-styled and a short-styled parent; and the 6 short-styled seedlings may be
attributed to reversion to their short-styled progenitor.
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