Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/153

. V. be little doubt, had I examined a young enough bud of Malaxis, I should have found a similar minute tongue-shaped cellular projection on the crest of the rostellum.

The anther opens widely whilst the flower is in bud, and then shrivels and contracts downwards, so that, when the flower is fully expanded, the pollinia are quite naked, with the exception of their broad lower ends, which rest in two little cups formed by the shrivelled anther-cells. This contraction of the anther is represented in fig. D in comparison with fig. C, which shows the state of the anther in a bud. The upper and much pointed ends of the polliniæ rest on, but project beyond, the crest of the rostellum; in the bud they are unattached, but by the time the flower opens they are always caught by the posterior surface of the drop of viscid matter, of which the anterior surface projects slightly beyond the face of the rostellum. That they are caught without any mechanical aid I ascertained by allowing some buds to open in my room. In fig. E the pollinia are shown exactly as they appeared (but not quite in their natural position) when removed by a needle from a specimen kept in spirits of wine, in which the irregular little mass of viscid matter had become hardened and adhered firmly to their tips.

The pollinia consist of two pairs of very thin leaves of waxy pollen; and the four leaves are formed of angular compound grains which never separate. As the pollinia are almost loose, being retained merely by the adhesion of their tips to the viscid fluid, and by their bases resting in the shrivelled anther-cells, and as the petals and sepals are much reflexed, the pollinia, when the flower is fully expanded, would have been liable to be blown away or out of their proper position,