Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/241

. VII. fig. 34; in which the pedicel of the pollinium has not as yet become separate from the rostellum, but the future line of separation is shown by a line (dotted in the figure) of hyaline tissue. The filament of the anther (f, fig. 34) has not as yet grown to its full length. When fully developed it bears two little leaf-like appendages which lie oh the anther. Lastly, on the sides of the stigma there are two slight protuberances (fig. 33), which apparently represent the antennæ of Catasetum, but have not the same function.

Neither the labellum nor the protuberances on the sides of the stigma are at all sensitive; but when on three occasions I momentarily touched the filament, between the little leaf-like appendages, the pollinium was ejected in the same manner and through the same mechanism as in Mormodes; but it was thrown only to the distance of about an inch. If the filament had been touched by an object which had not been quickly removed, or if by an insect, the viscid disc would certainly have adhered to it. Mr. Veitch informs me that he has often touched the end of the column, and the pollinium has adhered to his finger. When the pollinium is ejected, the pedicel forms a hoop, with the exterior surface of the curtain of the disc resting on and covering the anther. In about fifteen minutes the pedicel straightens itself, and the anther-case drops off; and now the pollinium is in a right position for fertilising another flower. As soon as the viscid matter on the under surface of the disc is exposed to the air it quickly changes colour and sets hard. It then adheres with surprising force to any object. From these various facts and from the analogy of the other Catasetidæ, we may conclude that insects visit the flowers for the sake of gnawing the labellum: