But the case is one merely of
great variability. The pollen-grains from the two sets of anthers, as observed
by Hildebrand and myself, do not differ in diameter. I fertilised twelve flowers
on several plants with pollen from a distinct plant, choosing those with pistils
of a different length; and 10 of these (i.e. 83 per cent) produced capsules,
which contained on an average 7.9 seeds. Fourteen flowers were fertilised with
their own pollen, and 11 of these (i.e. 79 per cent) yielded capsules,
containing a larger average of seed, namely 9.2. These plants, therefore, in
function show not the least sign of being heterostyled. I may add that 18
flowers protected by a net were left to fertilise themselves, and only 10 of
these (i.e. 55 per cent) yielded capsules, which contained on an average only
6.3 seeds. So that the access of insects, or artificial aid in placing pollen on
the stigma, increases the fertility of the flowers; and I found that this
applied especially to those having shorter pistils. It should be remembered that
the flowers hang downwards, so that those with short pistils would be the least
likely to receive their own pollen, unless they were aided in some manner.
Finally, as Hildebrand has remarked, there is no evidence that any of the
heterostyled species of Oxalis are tending towards a dioecious condition, as
Zuccarini and Lindley inferred from the differences in the reproductive organs
of the three forms, the meaning of which they did not understand.
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