In
Scrophularia aquatica the pistil is bent downwards from the mouth of the
corolla, but it thus strikes the pollen-dusted breast of the wasps which
habitually visit these ill-scented flowers. In all these cases we see the
supreme dominating power of insects on the structure of flowers, especially of
those which have irregular corollas. Flowers which are fertilised by the wind
must of course be excepted; but I do not know of a single instance of an
irregular flower which is thus fertilised.
Another point deserves notice. In each of the three forms two sets of stamens
correspond in length with the pistils in the other two forms. When bees suck the
flowers, the anthers of the longest stamens, bearing the green pollen, are
rubbed against the abdomen and the inner sides of the hind legs, as is likewise
the stigma of the long-styled form. The anthers of the mid-length stamens and
the stigma of the mid-styled form are rubbed against the under side of the
thorax and between the front pair of legs. And, lastly, the anthers of the
shortest stamens and the stigma of the short-styled form are rubbed against the
proboscis and chin: for the bees in sucking the flowers insert only the front
part of their heads into the flower. On catching bees, I observed much green
pollen on the inner sides of the hind legs and on the abdomen, and much yellow
pollen on the under side of the thorax.
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