Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/183

. VI. What can be the use, it may be asked, of a nectary of such disproportionate length? We shall, I think, see that the fertilisation of the plant depends on this length, and on nectar being contained only within the lower and attenuated extremity. It is, however, surprising that any insect should be able to reach the nectar. Our English sphinxes have proboscides as long as their bodies; but in Madagascar there must be moths with proboscides capable of extension to a length of between ten and eleven inches! This belief of mine has been ridiculed by some entomologists, but we now know from Fritz Müller that there is a sphinx-moth in South Brazil which has a proboscis of nearly sufficient length, for when dried it was between ten and eleven inches long. When not protruded it is coiled up into a spiral of at least twenty windings.

The rostellum is broad and foliaceous, and arches rectangularly over the stigma and over the orifice of the nectary: it is deeply notched by a cleft enlarged or widened at the inner end. Hence the rostellum nearly resembles that of Calanthe after the disc has been removed (see fig. 26, C). The under surfaces of both margins of the cleft, near their ends, are bordered by narrow strips of viscid membrane, easily removed; so that there are two distinct viscid discs. A short membranous pedicel is attached to the middle of the upper surface of each disc; and the pedicel carries a pollen-mass at its other end. Beneath the rostellum a narrow, ledge-like, adhesive stigma is seated.

I could not for some time underhand how the pollinia of this Orchid were removed, or how the stigma was fertilised. I passed bristles and needles