It is scarcely necessary to
give any additional evidence, but I may add that ten pots of Polyanthuses and
cowslips of both forms, protected from insects in my greenhouse, did not set one
pod, though artificially fertilised flowers in other pots produced an abundance.
We thus see that the visits of insects are absolutely necessary for the
fertilisation of Primula veris. If the corolla of the long-styled form had
dropped off, instead of remaining attached in a withered state to the ovarium,
the anthers attached to the lower part of the tube with some pollen still
adhering to them would have been dragged over the stigma, and the flowers would
have been partially self-fertilised, as is the case with Primula Sinensis
through this means. It is a rather curious fact that so trifling a difference as
the falling-off of the withered corolla, should make a very great difference in
the number of seeds produced by a plant if its flowers are not visited by
insects.
The flowers of the cowslip and of the other species of the genus secrete plenty
of nectar; and I have often seen humble bees, especially B. hortorum and
muscorum, sucking the former in a proper manner, though they sometimes bite
holes through the corolla. (1/5. H. Muller has also seen Anthophora pilipes and
a Bombylius sucking the flowers. 'Nature' December 10, 1874 page 111.
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