Abstract
THERE are two points in the structure of the heartsease (Viola tricolor) which are not mentioned in Mr. Bennett's interesting article on its fertilisation, but which, I think, deserve notice.* The first of these is the lip of the stigma, which closes the entrance to the spur and must be pushed back by an insect trying to reach the nectary, thereby bending down the head of the stigma, so as to sweep any pollen that may be adhering to those parts of the insect which come into contact with it into its receptacle; while, in withdrawing, the insect necessarily presses against the lower side of the lip, and raises up the whole stigma, thus rendering self-impregnation impossible, or at least highly improbable. Modifications of the same contrivance may be seen in many other flowers, e.g. Finguicula, Iris, &c.; it reaches, perhaps, its greatest perfection in Mimulus and Bignonia,† where, to the usual mechanical disposition of the parts, there is added irritability of the stigmatic lobes, which close together spontaneously when touched, expanding again after a while, if not already pollenated.‡
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HART, W. Fertilisation of the Wild Pansy. Nature 8, 121 (1873). https://doi.org/10.1038/008121a0
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DOI: https://doi.org/10.1038/008121a0
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