Two Kinds of Stamens with Different Functions in the same Flower

Abstract

IN NATURE, vol. xxiv. p. 307 is a very interesting letter on this subject, in which while the functions performed by the two kinds of stamens are very clearly indicated, the modus operandi of fertilisation, it appears to me, is less clearly expressed. I have witnessed in many instances the visitation by various species of large Hymenoptera, such as Xylocopa and Bombus, of species especially of the genus Melastoma, possessing stamens in all points corresponding to that occurring in the Heeria described in the letter referred to and what takes place seems to be as follows. The large bees eyidently make for the yellow platform offered by the short stamens, perhaps because they do not perceive the pistil and long stamens owing to their projection against the broad petaled corolla of the same colour in the background, and invariably receive the pistil between their legs, their feet settling on the fork of the connective, the instant effect of which is to collect the whole of the long stamens into a bunch, and to depress their anthers downwards and away from the body of the visiting bee, while the pistil remains in constant contact with its ventral side. At the moment of the bee's departure the hooks on the bee's feet by pulling on the connective fork raise the anthers of the long stamens, so as to bring the tips of the collected bunch into contact with its sides and abdomen. Dr. Muller's statement “by moving the connective fork of the larger ones” is somewhat ambiguous; for it is movement only in one direction that is of avail in raising the anthers of the larger stamens, pressure at the connective hook of course tends to depress the anthers and keep them apart from the bee's abdomen while a very slight backward pull at once raises the anther.