Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/278

258 single grains are embedded in a glutinous fluid; in all the other Orchids seen by me (except the degraded Cephalanthera) the grains are united three or four together. These compound grains are tied one to the other by elastic threads, but they often form packets which are tied together in like manner, or they are cemented into the so-called waxy masses. The waxy masses graduate in the Epidendreæ and Vandeæ from eight to four, to two, and, by the cohesion of the two, into a single mass. In some of the Epidendreæ we have both kinds of pollen within the same anther, namely, large waxy masses, and caudicles formed of elastic threads with numerous compound grains adhering to them.

I can throw no light on the nature of the cohesion of the pollen in the waxy masses; when they are placed in water for three or four days, the compound grains readily fall apart; but the four grains of which each is formed still firmly cohere; so that the nature of the cohesion in the two cases must be different. The elastic threads by which the packets of pollen are