Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/191

. VI. flowers being fertilised with pollen from a distinct plant.

With respect to Stanhopea, Dr. Crüger says that in the West Indies a bee (Euglossa) often visits the flowers for the sake of gnawing the labellum, and he caught one with a pollinium attached to its back; but he adds that he cannot understand how the pollen-masses are inserted into the narrow mouth of the stigma. With Stanhopea oculata I found that the pollinia could almost always be attached to my naked or gloved finger, by gently sliding it down the concave surface of the arched column; but this occurred only within a short time after the expansion of the flowers, whilst they are highly odoriferous. By again sliding my finger down the column, the pollinia were almost always rubbed off by the sharp edge of the stigmatic chamber, and were left adhering close to its entrance. Flowers thus treated occasionally, though rarely, yielded capsules. The removal of the pollinia from my finger seemed to depend on the existence of a point projecting beyond the viscid disc, and which I suspect is specially adapted for this purpose. If this be so, the pollen-masses must emit their tubes without being inserted into the stigmatic chamber. I may add that the pollen-masses shrink very little by being thoroughly dried, and could not in this state be easily inserted.

The entrance into the stigma is in like manner, as I hear from Fritz Müller, so much contracted in Cirrhæa and Notylia, which belong to another subdivision of the Vandeæ, that the pollinia can be inserted