It is a perennial, with a stout rootstock. With few exceptions the leaves are radical; they are heart-shaped, smooth, with untoothed edges, and on long stalks. The flowering stems are long, angular, with a stalkless leaf nearly half-way up. At the summit is the solitary large flower. The fine thick sepals are slightly conjoined at their bases, the petals white, veined and leathery. The ovary is large, and on its summit, without the intervention of a style, are the four rayed stigmas. Around the ovary are five stamens—there should be ten, but five have been transformed into scales, which alternate with the perfect stamens, and are fringed with white hairs, each ending in a yellow knob; on the face nearest the ovary each scale bears two small honey-secreting glands. The perfect stamens ripen in succession, and as each becomes mature, it raises itself until the anther comes on top of the stigma, but with its back to it. The front opens and discharges the pollen away from the stigma; but it falls where insects seeking the honeyed glands (using the ovary as a perch) will get it upon their forelegs, and so attach it to the stigmas of the next flower they visit.
Grass of Parnassus.
Parnassia palustris.
—Saxifragæ.—
Oat.
Avena sativa.
—Gramineæ.—
It flowers in August and September. This is the only British species.
Oat-grass (Avena sativa).
We have three British species of Wild Oat, but a knowledge of their structure and differences may be best obtained perhaps by a consideration of the cultivated Oat of our fields. It is indeed probable that the cereal oat is but a cultivated form of our Common Wild Oat (A. fatua), for Professor Buckman succeeded years ago in obtaining as the ninth generation from seeds of A. fatua good crops of the farmers’ varieties called White Tartarian and Potato Oats. It is known that oats shed in harvesting often degenerate into the wild forms. As a cereal the Oat does not appear to be nearly so ancient as wheat and barley, for it was not cultivated by the Hebrews, the Egyptians, Greeks or Romans.
The genus is distinguished by having its flowers in a lax-panicle, the spikelets borne principally upon long, slender stalks. Each spikelet contains two or more flowers, of which the upper one is usually imperfect, and each is armed with a long twisted and bent awn. There are two outer glumes, each flowering glume deeply notched, the awn arising from the bottom of the notch. The pale is two-nerved, the scales two-toothed, the stamens three. The ovary has a hairy top and two short styles with feathery stigmas. The fruit adheres to the glume.