When the flower opens, the saddle-shaped disc is set free by the rupture of the membrane of the rostellum. Then the rostellum, which projects into the minute round orifice of the nectary, is easily depressed by the proboscis of a moth, and as the now naked and sticky under-surface of the saddle-shaped disc is uncovered, it adheres to the proboscis, and is withdrawn with it into the air, carrying the two pollinia (fig. 80) on its exterior surface. Almost instantly the saddle is exposed to the air, a rapid movement takes place. The two flaps curl inwards (fig. 81), and embrace the proboscis, and the pollinia, at first parallel, become divergent. A second movement now takes place, which causes the divergent pollinia (fig. 81), which are at right angles to the proboscis, to sweep through ninety degrees towards the tip of the proboscis, so as to become depressed, and lie on each side of it. Hence, when a moth pushes its proboscis between the guiding ridges of the labellum into the nectary of another flower, the two thick ends of the pollinia will exactly strike against the two stigmas. These stigmas are so viscid that they hold and rupture the elastic threads which bind the packets of pollen grains together, and some dark green grains are seen even with the naked eye remaining on the two white stigmatic surfaces. In the Orchids, as in all other flowering plants, tubes sent out by the pollen grains penetrate through the stigmas, and fertilize the ovules in the twisted ovary. The double movement of the pollinia, while on the moth’s proboscis, is owing to the rapidity with which the viscid matter contracts and dries. Both butterflies and moths frequent this Orchis. Mr. Darwin enumerates twenty-three species of these insects which he had seen with the pollinia of the Orchis pyramidalis attached to their proboscides. Many had two or three pairs; the proboscis of the Acherontia had seven, and that of the Caradium had no less than eleven of these saddles attached at regular distances from top to bottom of its proboscis. Few of the species of Orchis are visited by bees.