In Pot 2 the two self-fertilised plants always
had an advantage, except whilst quite young over the two crossed plants.
As I wished to ascertain how these plants would behave during a second
growth, they were cut down close to the ground whilst growing freely.
The crossed plants now showed their superiority in another way, for only
one out of the seven was killed by the operation, whilst three of the
self-fertilised plants never recovered. There was, therefore, no use in
keeping any of the plants excepting those in Pots 1 and 3; and in the
following year the crossed plants in these two pots showed during their
second growth nearly the same relative superiority over the
self-fertilised plants as before.
Tropaeolum minus.
The flowers are proterandrous, and are manifestly adapted for
cross-fertilisation by insects, as shown by Sprengel and Delpino. Twelve
flowers on some plants growing out of doors were crossed with pollen
from a distinct plant and produced eleven capsules, containing
altogether twenty-four good seeds. Eighteen flowers were fertilised with
their own pollen and produced only eleven capsules, containing
twenty-two good seeds; so that a much larger proportion of the crossed
than of the self-fertilised flowers produced capsules, and the crossed
capsules contained rather more seed than the self-fertilised in the
ratio of 100 to 92. The seeds from the self-fertilised capsules were
however the heavier of the two, in the ratio of 100 to 87.
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