4. Grain.—Examine several kinds of grass “seeds” and make out that they not only consist of the entire ripened ovary and are therefore fruits, but that usually the pales also remain attached to them.
5. The embryo and endosperm.—Again cut through soaked grains of maize and wheat, and make out the embryo and endosperm ([p. 19]).
Grass flowers.—Grasses are true flowering plants; but because they depend on the wind for the transference of pollen to the stigmas, they do not pander to the taste of bees and butterflies by secreting nectar, and hence have no need to display those advertisement placards which we call petals. For this reason their flowers are not generally recognised as such. It requires a little care to make out the parts of the flower and to understand the manner in which the flowers are arranged among themselves.
Fig. 100—Diagram of a
Grass Spikelet. g, the
glumes; p₁ and p₂,
the outer and inner
pales; B, flower.
The whole group of flowers borne by any one haulm is generally called the ear or panicle. The ear in its turn consists of several bodies called spikelets. The appearance of the ear varies greatly in different grasses (Figs. 102 to 110) according as the stalks of the spikelets are long and spread outwards from the haulm, as in the meadow-grasses ([Fig. 103]), oats ([Figs. 99] and [ 108]), fescues ([Fig. 102]), and others; short, as in the foxtails ([Figs. 104 and 105]), timothy ([Fig. 106]), and sweet vernal grass ([Fig. 110]); or absent altogether, as in the wheat, barley, rye, rye grasses ([Fig. 109]), and couch grass.
A single spikelet of a grass is shown diagrammatically in [Fig. 100]. At the bottom are two boat-shaped bracts called glumes (g, g), which almost or entirely cover the spikelet before it opens. When the glumes have been removed a few flowers remain. Each one is protected by two leaves called pales: outer (p₁) and inner (p₂) respectively. The flower (B), as a rule, has three stamens, the anthers being borne on long filaments and dangling out to the wind ([Fig. 101]), and a pistil with two branching feathery stigmas. In many grasses the outer pale bears a bristle called an awn, well seen in “bearded” wheat, barley, and upright brome grass.
[Fig. 101], A, represents a single spikelet of meadow fescue, with two open flowers. The outer pales of this grass are not awned. [Fig. 101], B, shows a single flower of the same grass from which the outer pale has been removed. The two little scales seen in front of the ovary (and at e in [Fig. 100]) possibly represent all that is left of a perianth ([p. 121]).
Fertilisation.—By the time the flowers have opened, the haulm has usually grown so tall that they are lifted well above the leaves. The stamens hang their anthers loosely out to the wind, and, as the slender haulm sways in the breeze, the pollen is readily detached and carried to other flowers, perhaps miles away.