) Mr.
Scott experimented on P. Scotica, mollis, and verticillata, and found that their
flowers yielded an abundance of seeds when fertilised with their own pollen.
This shows that they are not heterostyled in function. P. Scotica is, however,
only moderately fertile when insects are excluded, but this depends merely on
the coherent pollen not readily falling on the stigma without their aid. Mr.
Scott also found that the capsules of P. verticillata contained rather more seed
when the flowers were fertilised with pollen from a distinct plant than when
with their own pollen; and from this fact he infers that they are sub-
heterostyled in function, though not in structure. But there is no evidence that
two sets of individuals exist, which differ slightly in function and are adapted
for reciprocal fertilisation; and this is the essence of heterostylism. The mere
fact of a plant being more fertile with pollen from a distinct individual than
with its own pollen, is common to very many species, as I have shown in my work
'On the Effects of Cross and Self-fertilisation.'
Hottonia palustris.
This aquatic member of the Primulaceae is conspicuously heterostyled, as the
pistil of the long-styled form projects far out of the flower, the stamens being
enclosed within the tube; whilst the stamens of the short-styled flower project
far outwards, the pistil being enclosed.
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