THE MEEK THAT INHERIT THE EARTH

Agnes Chase

OF ALL PLANTS the grasses are the most important to man. All our breadstuffs corn, wheat, oats, rye, barley and rice and sugarcane are grasses. Bamboos are grasses, and so are the Kentucky bluegrass and creeping bent of our lawns, the timothy and redtop of our meadows.

If such different-looking plants as bamboo, corn, and timothy are all grasses, what is it that characterizes a grass? It is the structure of the plant.

All grasses have stems with solid joints and two-ranked leaves, one at each joint. The leaves consist of two parts, the sheath, which fits around the stem like a split tube, and the blade, which commonly is long and narrow. No other plant family has just this structure. Clover and alfalfa, built on a very different plan, are not grasses. The seed heads of grasses are still more distinctive. The minute flowers are borne on tiny branchlets, often several crowded together, always two-ranked, like the leaves.

The grasses specialize in simplification; only rarely do they have nonessentials.

Being wind-pollinated, their flowers need no gay colors, no fragrance, no honey to attract insects. The flower consists of a single pistil with one ovule, two styles, each with a feathery stigma, and three (rarely one or six) stamens. Only three, or two, delicate little scales (lodicules) remain of the floral envelope, the calyx and corolla, of other flowers. These minute flowers are borne singly or two to many together in spikelets, which are really little flowering branches. The hypothetical flower-bearing branchlet is never elongated, as shown in figure 3 for the sake of comparison. The palea is immediately above the lemma, and the flower immediately above the palea. The axis of the spikelet (rachilla) is jointed as is the culm of a grass, and the lemmas (specialized leaves reduced to a bladelike sheath) are two-ranked as are the leaves.

The flowers have to do with perpetuating the species. Most grasses flower every year. But some perennials, which spread by specialized underground stems (rhizomes or rootstocks), may cover extensive areas, especially in salt or brackish marshes, without flowering regularly; bamboos flower mostly at intervals of a few to many years.

The root, stem, and leaves constitute the vegetative part of the plant, and are concerned with the life of the individual plant.

In grasses the vegetative parts are more uniform and characteristic than in most other families. If one has the stem and leaves of a plant, he can decide readily whether or not it is a grass. The only plants that may reasonably be mistaken for grasses are the sedges the culms are not jointed and are commonly three-sided, and the leaves are always three-ranked.

In grasses, specialization takes place mostly in the spikelet. By its vegetative characters a given plant is shown to be a grass, but it is the spikelets and their arrangement which indicate the kind of grass it is. The spikelet of cheat or chess (figure 5) is shown as seen naturally, the two glumes at the base, the florets (lemma, palea, and enclosed flower together) borne on opposite sides of the jointed rachilla, and the flower concealed. The palea with two nerves, its back to the rachilla, subtends and usually surrounds the flower. The glumes bear no flowers and are without paleas. This simple fundamental floral structure is subject to all manner of modification, but every organ found in the most highly specialized spike-let is to be interpreted as an elaboration or reduction of some part of this structure. The floret is the unit of the spikelet; the spikelet is the unit of the inflorescence.

The spikelets of wheat (figure 6) are sessile, that is, borne directly (without pedicel) on opposite sides of a stout axis, being placed flatwise against it; those of Italian ryegrass (figure 7) are borne in like manner but are placed edgewise to the axis.

In wild oats (figure 8) , the glumes are enlarged and the fertile florets are but two, with an additional sterile one. The lemmas bear a stout twisted bristle (awn) from the back near the base. In timothy (figure 9), the spikelet has but one floret, which is enclosed in a pair of rigid-pointed glumes. In bluejoint (figure 10), the one floret is surrounded by long silky hairs at the base and the lemma bears a slender awn from the back, and a segment of the rachilla is produced beyond the base of the palea, suggesting that this spike-let is derived from a form with more than one floret. In the needlegrasses, the lemma bears a stout twisted awn from the summit ( figure 11) , and in three-awn grasses the awn is divided into three branches ( figure 12).

[Top: The parts of a young shoot;

(2) The flower of a grass plant.]

In all grasses mentioned so far the structure is simple and all florets in a spikelet are alike. In some groups single spikelets may contain two very different kinds of florets, at least one perfect ( that is, enclosing a flower having stamens and pistil, and perfecting a grain) and one or more reduced sterile florets. The grama grasses (Bouteloua) have spikelets of this kind (figure 13). In this and allied genera the spikelets are borne in spikes; that is, sessile, as in wheat (figure 6) , but all on one side of the rachis, not on opposite sides as in wheat. ( The axis of a single spike or of a branching panicle is termed axis; that of a secondary spike or raceme is termed rachis.)

Diagram of leafy flowering branch, the flowers and bracts arranged as are those in grasses. Figure 4: Diagram of grass spikelets for comparison.