ced plants
are thus true hybrids (When Darwin wrote in reference to the different
forms of heterostyled plants, "which all belong to the same species
as certainly as do the two sexes of the same species" ("Cross and
Self fertilisation", page 466), he adopted the term species in a
comprehensive sense. The recent researches of Bateson and Gregory ("On
the inheritance of Heterostylism in Primula"; "Proc. Roy. Soc." Ser. B,
Vol. LXXVI. 1905, page 581) appear to me also to support the view that
the results of illegitimate crossing of heterostyled Primulas correspond
with those of hybridisation. The fact that legitimate pollen effects
fertilisation, even if illegitimate pollen reaches the stigma a short
time previously, also points to this conclusion. Self-pollination in the
case of the short-styled form, for example, is not excluded. In spite
of this, the numerical proportion of the two forms obtained in the open
remains approximately the same as when the pollination was exclusively
legitimate, presumably because legitimate pollen is prepotent.), with
which their behaviour in other respects, as Darwin showed, presents so
close an agreement. This view receives support also from the fact that
descendants of a flower fertilised illegitimately by pollen from another
plant with the same form of flower belong, with few exceptions, to the
same type as that of their parents. The two forms of flower, however,
behave differently in this respect. Among 162 seedlings of the
long-styled illegitimately pollinated plants of Primula officinalis,
including five generations, there were 156 long-styled and only six
short-styled forms, while as the result of legitimate fertilisation
nearly half of the offspring were long-styled and half short-styled. The
short-styled illegitimately pollinated form gave five long-styled
and nine short-styled; the cause of this difference requires further
explanation. The significance of heterostyly, whether or not we now
regard it as an arrangement for the normal production of hybrids, is
comprehensively expressed by Darwin: "We may feel sure that plants have
been rendered heterostyled to ensure cross-fertilisation, for we now
know that a cross between the distinct individuals of the same species
is highly important for the vigour and fertility of the offspring."
("Forms of Flowers", page 258.) If we remember how important the
interpretation of heterostyly has become in all general problems as,
for example, those