Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/49

. I. and would consequently be rarely visited by insects. I then looked at the perfectly healthy plant under the bell-glass, and it had, of course, all its pollinia in the anther-cells. I tried an analogous experiment with specimens of O. mascula with the same result. It deserves notice that the spikes which had been covered up, when subsequently left uncovered, never had their pollinia carried away by insects, and did not, of course, set any seed, whereas the adjoining plants produced plenty of seed. From this fact it may be inferred that there is a proper season for each kind of Orchis, and that insects cease their visits after the proper season has passed.

With many of the hitherto mentioned species, and with several other European kinds, the sterility of the flowers, when protected from the access of insects, depends solely on the pollen-masses not coming into contact with the stigma. This has been proved to be the case by Dr. Hermann Müller, who, as he informs me, applied the pollen-masses of Orchis pyramidalis (44), fusca (6), militaris (14), variegata (3), coriophora (6), morio (4), maculata (18), mascula (6), latifolia (8), incarnata (3), Ophrys muscifera (8), Gymnadenia conopsea (14), albida (8), Herminium monorchis (6), Epipogon aphyllus (2), Epipactis latifolia (14), palustris (4), Listera ovata (5), and Cypripedium calceolus (2), to their own stigmas, and full-sized capsules, containing seeds in appearance good, were formed. The numbers placed after the names of the species show how many flowers were tried in each case. These facts are remarkable, because Mr. Scott and Fritz Müller have proved