Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/290

270 is covered with longitudinal, fimbriated ridges. In several species of Ophrys, there are two small shining protuberances, at the base of the labellum, beneath the two discs. Innumerable other cases could be added of the presence of singular and diversified excrescences on the labellum; and Lindley remarks that their use is quite unknown.

From the position, relatively to the viscid discs, which these excrescences occupy, and from the absence of any free nectar, it formerly seemed to me highly probable that they afforded food and thus attracted either Hymenoptera or flower-feeding Coleoptera. There is no more inherent improbability in a flower being habitually fertilised by an insect coming to feed on the labellum, than in seeds being habitually disseminated by birds attracted by the sweet pulp in which they are embedded. But I am bound to state that Dr. Percy, who had the thick and furrowed labellum of a Warrea analysed for me by fermentation over mercury, found that it gave no evidence of containing more saccharine matter than the other petals. On the other hand, the thick labellum of Catasetum and the bases of the upper petals of Mormodes ignea, have a slightly sweet, rather pleasant, and nutritious taste. Nevertheless, it was a bold speculation that insects were attracted to the flowers of various Orchids in order to gnaw the excrescences or other parts of their labella; and few things have given me more satisfaction than the full confirmation of this view by Dr. Crüger, who has repeatedly witnessed in the West Indies humble-bees of the genus Euglossa gnawing the labellum of Catasetum, Coryanthes, Gongora, and Stanhopea. Fritz Müller also has often found, in