Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/102

82 from the anther-cells, being tied to the edge of the stigma and supported by the penetration of the pollen-tubes. Without this support the pillars would soon fall down.

The flower stands upright, with the lower part of the labellum turned up parallel to the column (fig. A). The tips of the lateral petals never become separated; so that the pillars of pollen are protected from the wind, and as the flower stands upright they do not fall down from their own weight. These are points of much importance to the plant, as otherwise the pollen would have been blown or fallen down and been wasted. The labellum is formed of two portions; when the flower is mature, the small triangular distal portion turns down at right angles to the basal portion; and thus offers a small landing-place for insects in front of the triangular entrance, situated half-way up the almost tubular flower. After a short time, as soon as the flower is fully fertilised, the small distal portion of the labellum rises up, shuts the triangular door, and again perfectly encloses the organs of fructification.

Although I have often searched for nectar within the cup of the labellum, I have never found even a trace. The terminal portion of the labellum is frosted with globular papillæ of an orange colour, and within the cup there are several transversely wrinkled, longitudinal ridges of a darker orange tint. These ridges are often gnawed by some animal, and I have found minute, bitten-off fragments lying within the base of the cup. In the summer of 1862 the flowers were visited less frequently by insects than is usual, as shown by the unbroken state of the pollen-masses; nevertheless,