Thus, when the pistil first
escapes from the keel, the stigma is rubbed against the back of the bee,
dusted with pollen from the longer stamens, either of the same or
another flower; and afterwards against the lower surface of the bee
dusted with pollen from the shorter stamens, which is often shed a day
or two before that from the longer stamens. (5/16. These observations
have been quoted in an abbreviated form by the Reverend G. Henslow, in
the 'Journal of Linnean Society Botany' volume 9 1866 page 358. Hermann
Muller has since published a full and excellent account of the flower in
his 'Befruchtung' etc. page 240.) By this mechanism cross-fertilisation
is rendered almost inevitable, and we shall immediately see that pollen
from a distinct plant is more effective than that from the same flower.
I need only add that, according to H. Muller, the flowers do not secrete
nectar, and he thinks that bees insert their proboscides only in the
hope of finding nectar; but they act in this manner so frequently and
for so long a time that I cannot avoid the belief that they obtain
something palatable within the flowers.
If the visits of bees are prevented, and if the flowers are not dashed
by the wind against any object, the keel never opens, so that the
stamens and pistil remain enclosed. Plants thus protected yield very few
pods in comparison with those produced by neighbouring uncovered bushes,
and sometimes none at all.
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