O150s swelling), a cereal (Avena sativa) belonging to the tribe Avenece of the order Gramineae or grasses.
In tropical regions, where Leguminosae is the leading order, grasses closely follow as the second, whilst in the warm and temperate regions of the northern hemisphere, in which Compositae takes the lead, Gramineae again occupies the second position.
Yet the first attempts at a classification of plants recognized and separated a group of Gramina, and this, though bounded by nothing more definite than habit and general appearance, contained the Gramineae of modern botanists.
This character is absolute for the whole order, and effectually separates Gramineae from Cyperaceae.
Comparing the flower of Gramineae with the general monocotyledonous plan as represented by Liliaceae and other families (fig.
Compositae are comparatively rare; so also Gramineae and Cyperaceae are in some places deficient, and Labiatae, Leguminosae and ferns in others.
Best distinctions are found in the position of the embryo in relation to the endosperm - lateral in grasses, basal in Cyperaceae - and in the possession by Gramineae of the 2-nerved palea below each flower.
In number of species Gramineae comes considerably after Compositae and FIG.
It is based upon the fact that the histological differentiation of the epidermis of their root is that generally characteristic of Monocotyledons, whilst they have two cotyledons - the old view of the epiblast as a second cotyledon in Gramineae being adopted.
Leguminosae, the two most numerous orders of phanerogams, but in number of individual plants it probably far exceeds either; whilst from the wide extension of many of its species, the proportion of Gramineae to other orders in the various floras of the world is much higher than its number of species would lead one to expect.