§ 2 Action of Pollen, and Formation of the Embryo
343. Pollen-growth. A grain of pollen may be justly likened to one of the simple bodies (spores) which answer for seeds in Cryptogamous plants. Like one of these, it is capable of germination. When deposited upon the moist surface of the stigma (or in some cases even when at a certain distance) it grows from some point, its living inner coat breaking through the inert outer coat, and protruding in the form of a delicate tube. This as it lengthens penetrates the loose tissue of the stigma and of a loose conducting tissue in the style, feeds upon the nourishing liquid matter there provided, reaches the cavity of the ovary, enters the orifice of an ovule, and attaches its extremity to a sac, or the lining of a definite cavity, in the ovule, called the Embryo-Sac.
344. Origination of the Embryo. A globule of living matter in the embryo-sac is formed, and is in some way placed in close proximity to the apex of the pollen tube; it probably absorbs the contents of the latter; it then sets up a special growth, and the Embryo (8-10) or rudimentary plantlet in the seed is the result.
Footnotes
1 Beginning with one by C. C. Sprengel in 1793, and again in our day with Darwin, “On the Various Contrivances by which Orchids are fertilized by Insects,” and in succeeding works.