Thirdly, the plants of Nicotiana on which I experimented appear to come
under the present class of cases; for they varied in their sexual
constitution and were more or less highly self-fertile. They were
probably the offspring of plants which had been spontaneously
self-fertilised under glass for several generations in this country. The
flowers on the parent-plants which were first fertilised by me with
their own pollen yielded half again as many seeds as did those which
were crossed; and the seedlings raised from these self-fertilised seeds
exceeded in height those raised from the crossed seeds to an
extraordinary degree. In the second and third generations, although the
self-fertilised plants did not exceed the crossed in height, yet their
self-fertilised flowers yielded on two occasions considerably more seeds
than the crossed flowers, even than those which were crossed with pollen
from a distinct stock or variety.
Lastly, as certain individual plants of Reseda odorata and lutea are
incomparably more self-fertile than other individuals, the former might
be included under the present heading of the appearance of new and
highly self-fertile varieties. But in this case we should have to look
at these two species as normally self-sterile; and this, judging by my
experience, appears to be the correct view.
We may therefore conclude from the facts now given, that varieties
sometimes arise which when self-fertilised possess an increased power of
producing seeds and of growing to a greater height, than the
intercrossed or self-fertilised plants of the corresponding
generation--all the plants being of course subjected to the same
conditions.
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