Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/174

154 it is almost cylindrical (fig. C) but often of the most diversified shapes. The pedicel is generally nearly straight, but in Miltonia clowesii it is naturally curved; and in some cases, as we shall immediately see, it assumes, after removal, various shapes. The extensible and elastic caudicles, by which the pollen-masses are attached to the pedicel, are barely or not at all visible, being embedded in a cleft or hollow within each pollen-mass. The disc, which is viscid on the under side, consists of a piece of thin or thick membrane of

.



.

varied forms. In Acropera it is like a pointed cap; in some cases it is tongue-shaped, or heart-shaped (fig. C), or saddle-shaped, as in some Maxillarias, or like a thick cushion (fig. A), as in many species of Oncidium, with the pedicel attached at one end, instead of, as is more usual, nearly to the centre. In Angræcum distichum and sesquipedale the rostellum is notched, and two separate, thin, membranous discs can be removed, each carrying by a short pedicel a pollen-mass. In Sarcanthus teretifolius the disc (fig. D) is