Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/71

. II. capsule, though near Florence rather more capsules are produced. The labellum does not secrete any nectar. The flowers, however, must be occasionally visited and fertilised by insects, for Delpino found pollen-masses on the stigmas of some flowers which still retained both their own pollinia.

The anther-cells are remarkably open, so that with some plants which were sent me in a box, two pair of pollinia fell out, and stuck by their viscid discs to the petals. Here we have an instance of the first appearance of a trifling structure which is of not the least use to its possessor, but becomes when a little more developed, highly beneficial to a closely-allied species; for although the open state of the anther-cells is useless to the Spider Ophrys, it is of the highest importance, as we shall presently see, to the Bee Ophrys. The flexure of the upper end of the caudicle of the pollinium is of service to the Spider and Fly Ophrys, by aiding the pollen-masses, when carried by insects to another flower, to strike the stigma; but by an increase of this bend together with increased flexibility in the Bee Ophrys, the pollinia become adapted for the widely different purpose of self-fertilisation.

Ophrys arachnites.—This form, of which Mr. Oxenden sent me several living specimens, is considered by some botanists as only a variety of the Bee Ophrys, by others as a distinct species. The anther-cells do not stand so high above the stigma, and do not overhang it so much, as in the Bee Ophrys, and the pollen masses are more elongated. The caudicle is only two-thirds, or even only half as long as that of the Bee