Fig. 92. Staminate Squash flower.
The pollen is nearly always in the form of very small grains, which become dry when ripe. In some plants, notably in orchids, the pollen is borne in large masses known as pollinia. When the anther is “ripe” it assumes a yellow, orange or brownish cast and the pollen is discharged through a split in the side, a chink at the apex or other aperture. The pollen may fall upon and fertilize the stigma of the same flower, in which case the flower is said to be self-fertilized, or oftener it is carried to another flower by insects, winds or other agencies. Most plants possess some contrivance which renders self-fertilization difficult and cross-fertilization easy.
Fig. 93. Closed stigma of tecoma.
Fig. 94. Open stigma of tecoma.