These fifteen species consist of
Brassica oleracea, Reseda odorata and lutea, Limnanthes douglasii,
Papaver vagum, Viscaria oculata, Beta vulgaris, Lupinus luteus, Ipomoea
purpurea, Mimulus luteus, Calceolaria, Verbascum thapsus, Vandellia
nummularifolia, Lactuca sativa, and Zea mays.) For instance, with
Ipomoea purpurea every single intercrossed plant exceeded in height its
self-fertilised opponent until the sixth generation; and so it was with
Mimulus luteus until the fourth generation. Out of six pairs of crossed
and self-fertilised cabbages, every one of the former was much heavier
than the latter. With Papaver vagum, out of fifteen pairs, all but two
of the crossed plants were taller than their self-fertilised opponents.
Of eight pairs of Lupinus luteus, all but two of the crossed were
taller; of eight pairs of Beta vulgaris all but one; and of fifteen
pairs of Zea mays all but two were taller. Of fifteen pairs of
Limnanthes douglasii, and of seven pairs of Lactuca sativa, every single
crossed plant was taller than its self-fertilised opponent. It should
also be observed that in these experiments no particular care was taken
to cross-fertilise the flowers immediately after their expansion; it is
therefore almost certain that in many of these cases some pollen from
the same flower will have already fallen on and acted on the stigma.
There can hardly be a doubt that several other species of which the
crossed seedlings are more vigorous than the self-fertilised, as shown
in Tables 7/A, 7/B and 7/C, besides the above fifteen, must have
received their own pollen and that from another plant at nearly the same
time; and if so, the same remarks as those just given are applicable to
them.
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