166 GRASSES GRASSES, plants of the natural order grami- nea, one of the most extensive in number of species and individuals, and one of the most im- portant in its relation to man. The stem (culm) is jointed, sometimes solid, but usually hollow, and closed at the joints (nodes) ; from each joint rises a leaf stalk which is broad and en- velops the stem, called the sheath (vagina), which with few exceptions is split upon one side for its whole length ; at the apex of the sheaths are borne the leaves, which are alter- nate, the blade (lami- na) usually narrow, and with parallel veins; where the blade and sheath join is a small membranous appen- dage, the ligule, which is sometimes represent- ed by a fringe of hairs. The flowers are ar- ranged at the summit of the stem in strict spikes, racemes, or loose panicles, and are in spikelets, which con- F,o. i.-Phienm, .pikelet * of one or numerous flowers (florets). The parts of the flowers are chaffy, usually green when young and becoming straw-colored at maturity, and are described collectively as glumaceous (Lat. gluma, a husk), a term also applied to the flowers of some allied families. In structure the flowers present some very complex forms, while that in the more com- mon species is exceedingly simple, and may be readily understood by an examination of the common red-top, a species of agro&tis, or timo- thy (pTileum to be found almost everywhere. A single spikelet of either of these will be found, as in the engraving of phleum, to con- sist of two concave scales called glumes, one placed slightly above and within the other; within these are the floret, consisting also of two scales, and the palets, the upper and inner of which is more or less covered by the outer, and usually smaller and of more delicate tex- ture ; the essential parts of the flower are within and pro- tected by the palets ; the stamens, one to six (usually three), have slender filaments with anthers attached l.y the middle (versa- tile); pistil one, with a one-celled, one-ovul- ed ovary crowned by Fiu . 2..^ ikelet two (rarely three) the stigmas of which are feathery or biury; the ovary in ripening becomes a grain (caryopsis), which consists of the usually adhe- rent pericarp (the hull), within which is the seed proper, consisting of a small embryo situated at the base and on the outside of a floury albumen ; at the base of the pistil are situated one or two minute scales (lodiculas), which are usually so small as to escape the notice of a careless ob- server, but in some genera are as long as the ovary. This is the general structure of one- flowered grasses, but it is varied in different genera by the suppression of the upper palet, or even by the absence of both glumes, and the prolongation of the apex of one or both glumes or the lower palet into a bristle-like appendage, the awn. In the many-flowered grasses, of which hair grass (aira) will serve as a familiar illustration, there are two glumes, and within these two to several florets placed one above another upon a short axis (rachis), all of which except the upper one contain stamens and a pistil ; the uppermost floret in the oat and in many other many-flowered grasses is neutral or imperfect ; the lower palet in the oat is strongly many-nerved, and bears below its apex a strong and twisted awn. The nu- FIG. 8. Poa, spikelet. FIG. 4. Anthoxanthuin, spikelet. merous species of poa, including the meadow- grasses, June grass, blue grass, &c., afford ex- amples of many-flowered grasses in which the spikelets are compressed, the palets without awns, and more or less clothed with cottony hairs. The suborders of the family and the genera are founded upon various modifications of a very simple structure, some of which have been here indicated. In the sweet-scented ver- nal grass we have another modification ; this grass appears to be one-flowered, but it is real- ly three-flowered, with the upper and lower florets abortive and appearing one on each side of the perfect one as an awned empty palet. In barley (hordeum) and wheat (triticum) the spikelets are sessile in the excavations of a zig- zag stem or rachis; in the barley the spikelets are one-flowered, only the central one some^ times being fertile, as in two-rowed barley, and at others all three being fertile, when the spike or head becomes six-rowed, and the glumes are placed upon the side of the spike- lets opposite the stem and form a bristle-like involucre. Grasses are annuals or perennials, and in some of the perennial species the root stock runs for a long distance underground, as in the couch grass, or "quack" (triticum repens), which often becomes a serious pest to the cul-
