Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/214

C. saccatum. In other respects there is no important difference. The antennæ are of greater length; their tips for about one-twentieth of their length are roughened by cells produced into papillæ.

Fig. 30.

Catasetum tridentatum.

pd.a. anther.

pd. pedicel of pollinium.

pd.an. antennæ.

pd.l. labellum.

A. Side view of flower in its natural position, with two of the sepals cut off.

B. Front view of column, in position reverse of fig. A.

The pedicel of the pollinium is articulated as before by a hinge to the disc; it can move freely only in one direction owing to one end of the disc being upturned, and this restricted power of movement apparently comes into play when the pollinium is carried by an insect to the female flower. The disc is, as in the other species, of large size, and the end which when ejected first strikes any object, is much more viscid than the rest of the surface. This latter surface is drenched with a milky fluid, which, when exposed to the air, rapidly turns brown, and sets into a cheesy consistence. The upper surface of the disc consists of strong mem-