Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/285

. IX. elaborate mechanism for the ejection and transportal of the pollinia of Catasetum, with the sensitive rostellum so wonderfully modified, with the sexes borne on distinct plants, we may perhaps give the palm of victory to this genus.

SECRETION OF NECTAR.

Many Orchids, both our native species and the exotic kinds cultivated in our hothouses, secrete a copious supply of nectar. I have found the horn-like nectaries of Aerides filled with fluid; and Mr. Rodgers, of Sevenoaks, informs me that he has taken crystals of sugar of considerable size from the nectary of A. cornutum. The nectar-secreting organs of the Orchideæ present great diversities of structure and position in the various genera; but are almost always situated towards the base of the labellum. In Disa, however, the posterior sepal alone, and in Disperis the two lateral sepals together with the labellum, secrete nectar. In Dendrobium chrysanthum the nectary consists of a shallow saucer; in Evelyna, of two large united cellular balls; and in Bolbophyllum cupreum, of a medial furrow. In Cattleya the nectary penetrates the ovarium. In Angræcum sesquipedale it attains the astonishing length of above eleven inches; but I need not enter on further details. The fact, however, should be recalled, that in Coryanthes the nectar-secreting glands pour forth an abundance of almost pure water, which drips into a bucket formed by the distal part of the labellum; and this secretion serves to prevent the bees which come to gnaw the surface of the labellum from flying away, and thus compels them to crawl out through the proper passage.

Although the secretion of nectar is of the highest