Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/217

. VII. he was surprised at the gigantic seed-vessels of the Monachanthus; and he correctly remarks that "here we have traces of sexual difference in Orchideous flowers." Dr. Crüger also informs me that in Trinidad he never saw capsules naturally produced by the flowers of this Catasetum; nor when they were fertilised by him with their own pollen, as was done repeatedly. On the other hand, when he fertilised the flowers of the Monachanthus viridis with pollen from the Catasetum, the operation never failed. The Monachanthus also commonly produces fruit in a state of nature.

From what I had myself observed, I was led to examine carefully the female organs of C. tridentatum, callosum, and saccatum. In no case was the stigmatic surface viscid, as it is in all other Orchids (except as we shall hereafter see in Cypripedium), and as is indispensable for securing the pollen-masses by the rupture of the caudicles. I carefully looked to this point both in young and old flowers of C. tridentatum. When the surface of the stigmatic chamber and of the stigmatic canal of the above-named three species is scraped off, after having been kept in spirits, it is found to be composed of utriculi (including nuclei of the proper shape), but not nearly so numerous as with ordinary Orchids. The utriculi cohere more together