Page:On the Various Contrivances by Which British and Foreign Orchids are Fertilised by Insects, and on the Good Effects of Intercrossing.djvu/60



In front, in the middle of the column (Fig. A), the deep stigmatic chamber (s) may be seen; this is shown in the section (Fig. XXVI. C), in which all the parts are a little separated from each other, in order that the mechanism may be made intelligible. In the middle of the roof of the stigmatic chamber, far back (d, in A), the upturned anterior end of the viscid disc of the pollinium may be discerned. The disc is continuous on each side with a little fringe of membrane, which joins the bases of the two antennae. Over the disc the protuberant heart-shaped rostellum projects, and this is closely covered by a thin membrane. This membrane is the pedicel of the pollinJure, with its lower end attached (ped in sect. C, and in A) to the superior surface of the viscid disc, and with its upper end running under the anther-cells (a), and there united to the two pollen-masses. In its natural position the pedicel lies much bowed round the protuberant rostellum; when freed it forcibly straightens itself, and at the same time its lateral edges curl inwards. In the bud, at an early period of growth, the membranous pedicel forms part of the rostellum, but subsequently becomes separated from it by the solution of a layer of cells.