On The Origin of Species by Charles Darwin Chapter 16 Page 36

PLUMULE (in plants). — The minute bud between the seed-leaves of newly-germinated plants.

PLUTONIC ROCKS. — Rocks supposed to have been produced by igneous action in the depths of the earth.

POLLEN. — The male element in flowering plants; usually a fine dust produced by the anthers, which, by contact with the stigma effects the fecundation of the seeds. This impregnation is brought about by means of tubes (POLLEN-TUBES) which issue from the pollen-grains adhering to the stigma, and penetrate through the tissues until they reach the ovary.

POLYANDROUS (flowers). — Flowers having many stamens.

POLYGAMOUS PLANTS. — Plants in which some flowers are unisexual and others hermaphrodite. The unisexual