Fig. 77. Orchis pyramidalis:—Front view of flower with upper sepal and petals removed; a, anther; s, stigma; r, rostellum; l, labellum.
The Orchis pyramidalis is considered by Mr. Darwin to be the most highly organized species of the British Orchids he has examined. It has sharp leaves, and a close pyramid of white or rose-coloured blossoms. The upper sepal and the two upper petals form a hood, protecting the anther and stigmatic surfaces from the weather. In [fig. 77], a front view of a blossom, these are cut off as well as in [fig. 78] a, which represents a side view of the same blossom deprived of half the labellum, and the upper part of the nectary, or spur. The labellum is long, with three equal entire lobes, and is produced into an awl-shaped spur, or nectary. It has a small ridge on each side of its narrow base to guide the proboscides of insects to the mouth of the nectary, which, besides being small, is partially closed by the pouch-shaped rostellum, which is placed very low in this species, and is flanked on each side by a distinct stigmatic rounded surface ([fig. 77] s s). The rostellum (r) is hollowed out on its under-side in the middle, and is filled with a fluid. Instead of two little viscid discs or balls, as in the Orchis mascula, there is but one which is saddle-shaped ([figs. 78], [79]), carrying on its nearly flat top or seat, the two stalks of the pollinia, of which the two truncated ends firmly adhere to its upper-surface. Before the membrane of the rostellum ruptures, the saddle-shaped disc forms part of its continuous surface. The upper membrane of the disc is rather thick; it is lined with a layer of highly adhesive matter formed within the rostellum.
Fig. 78. Orchis pyramidalis:—Side view of flower, with a portion cut away; a, anther; r, rostellum; l, labellum; n, nectary.
Fig. 79. Disc of Orchis pyramidalis seen from above, with one pollinium, flattened by force.
Fig. 80. Pollinia of Orchis pyramidalis, attached to saddle-shaped disc.
