Part 143. The grass family (Graminae). Examples: oat (Fig. 1-4), rice (Figs. 5, 6), rye (Fig. 7), wheat (Figs. 8, 9), barleys (Figs. 10-12), maize (Figs. 13-15), sugar-cane (Fig. 114), broom-corn (Fig. 222), and bamboo (Fig. 224,).

Formulas of Zea, Saccharinum, Andropogon, Oryza, Avena, Secale, Triticum, Hordeum, Bambusa, and Gramineae are shown on pages 420-423.

The grasses introduce us to a new sub-class, characterized partly, as we shall see, by having the leaf-veins running in a regular, more or less parallel system. Leaves with such a framework are said to be parallel-veined. Grass leaves always have the veins running lengthwise from base to tip.

Other noteworthy features of grass leaves are that the base is wrapped about the stem so as to form a sheath the edges of which overlap as shown in Fig. 13; and the blades extend from only two sides of the stem, thus coming into two vertical ranks.

Most grass stems are round and hollow like straws. Rarely, as in the stalk of maize, there is a solid cylinder of pith, through which run scattered bundles of firmer, more or less woody material, not forming true rings, but often so crowded toward the surface as to constitute a somewhat bark-like zone. From an erroneous idea that these scattered bundles originated near the center of the stem and were forced outward by new growth, all stems with scattered bundles were early described as "inside-growing" or endogenous 1-a term still used conveniently, however, by way of contrast for stems of seed-plants of the non-exogenous type.

1 En-dog'en-ous - Gr. endos, within.

The bracts and bractlets of grasses in general are comparatively thin and stiff, like the husks or chaff of grain, and have received the special name of glumes.2

2 Glume - L. gluma, husk of corn.

The grain-like fruit of typical grasses resembles an achene in being the product of a simple pistil with one ovule and in being dry and indehiscent. It differs mainly in having the seed-coat adherent to the pericarp. A fruit of this kind is distinguished as a caryopsis.3

3 Car"y-op'sis - Gr. karyon, nut; opsis, resemblance.

As shown in Fig. 9 the embryo is placed at one side of the albumen. On the side toward the seed-food is a somewhat shield-shaped organ, termed the scutellum,4 through which the germ absorbs its nutriment when sprouting. Morphologically the scutellum is regarded by most botanists as the cotyledon of the embryo, enlarged and otherwise modified for its peculiar function. Unlike the embryo of dicotyledonous plants, the embryo of a grass, as of all the sub-class of seed-plants now to be studied, has but one cotyledon and is hence described as monocotyledonous.5

4 Scu-tel'lum - L. a little shield.

5 Mo"no-cot"y-led'on-ous - Gr. monos, one.

Grasses may be easily recognized as mostly herbs with hollow, cylindrical stems; parallel-veined, two-ranked sheathing leaves; flowers enclosed by glumaceous bracts; and fruit a caryopsis.

Part 144. The Grass Order

Part 144. The grass order (Graminales or Glumiflorae) comprises grass-like plants ivith glumaceous bracts, a one-celled superior ovary, and a solitary ovule.

The formula of Graminales is given on pages 422, 423.