Of the fruits produced 233 were
collected (many being left ungathered), and these included on an average 1.82
seed. No less than 16 out of the 233 fruits included the highest possible number
of seeds, namely 4, and 31 included 3 seeds. So we see how highly fertile these
short-styled plants were when illegitimately fertilised with their own-form
pollen by the aid of bees.
The great difference in the fertility of the long and short-styled flowers, when
both are illegitimately fertilised, is a unique case, as far as I have observed
with heterostyled plants. The long-styled flowers when thus fertilised are
utterly barren, whilst about half of the short-styled ones produce capsules, and
these include a little above two-thirds of the number of seeds yielded by them
when legitimately fertilised. The sterility of the illegitimately fertilised
long-styled flowers is probably increased by the deteriorated condition of their
pollen; nevertheless this pollen was highly efficient when applied to the
stigmas of the short-styled flowers. With several species of Primula the short-
styled flowers are much more sterile than the long-styled, when both are
illegitimately fertilised; and it is a tempting view, as formerly remarked, that
this greater sterility of the short-styled flowers is a special adaptation to
check self-fertilisation, as their stigmas are eminently liable to receive their
own pollen.
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