Order VI. Gramineae, R. Brown.—Grasses.
Gramina, Juss.—Graminaceae, Lind.
Characters.—Flowers usually hermaphrodite, sometimes monoecious or polygamous; consisting of imbricated bracts, of which the most exterior are called glumes, the interior immediately enclosing the stamens paleae, and the innermost at the base of the ovary scales. Glumes usually 2, alternate sometimes single; most commonly unequal. Paleae two, alternate; the lower or exterior simple; the upper or interior composed of 2, united by their contiguous margins, and usually with 2 keels, together forming a kind of dislocated calyx. Scales 2 or 3, sometimes wanting; if 2, collateral, alternate with the paleae, and next the lower of them, either distinct or united. Stamens hypogynous, 1, 2, 3, 4, 6, or more, 1 of which alternates with the 2 hypogynous scales, and is, therefore, next the lower paleae; anthers versatile. Ovary simple: styles 2 or 3, very rarely combined into 1; stigmas feathery and hairy; ovule ascending by a broad base, anatropal. Pericarp usually undistinguishable from the seed, membranous. Albumen farinaceous; embryo lying on one side of the albumen at the base, lenticular, with a broad cotyledon and a developed plumule; and occasionally, but very rarely, with a second cotyledon on the outside of the plumule, and alternate with the usual cotyledon.—Evergreen herbs. Rhizoma fibrous or bulbous. Stems cylindrical, usually fistular, closed at the joints, covered with a coat of silex, sometimes solid. Leaves narrow and undivided, alternate, with a split sheath, and a membranous expansion (ligula) at the junction of stalk and blade. Flowers in little spikes, called locustae, arranged in a spiked, racemed, or panicled manner (Lindley).
Properties.—Considered with reference to their ultimate or mineral constituents, the grasses are remarkable for the large proportion of silica, potash, and phosphoric acid, and for the small proportion of chlorine which they contain. The silica predominates in the leaves and stem, the phosphoric acid in the seeds. The following table [Drawn up fromthe calculated means contained in Johnston's Lectures on Agricultural Chemistry and Geology, 2d edit. 1847.] represents the mean composition of the ashes of the most important cereal grains.
Mean per centage Composition of the Ash of the following cereal Grains:—
||Wheat.||Barley (with the husk).||Oat.||Rye.||Indian corn.||Rice.|
|Oxide of iron||0.67||1.48||0.40||1.36||0.30||0.45|
|Per centage of ash||about 2.0||2.84||2.18||2.425||about 1.5||1.00|
The following table, drawn up by M.Payen [Précis de Chimie Industrielle, p. 394, Paris, 1849.], shows the properties of the proximate or immediate principles of the cereal grains:—
|100 parts of||Starch.||Gluten, and other Azotized Matters. ||Dextrine. Glucose, or Congenerous Substances.||Fatty Matters.||Cellulose.||Silica, Phosphates of Lime, Magnesia, and Soluble Salts of Potash and Soda.|
|Wheat, hard, of Venezuela||58.12||22.75||9.50||2.61||4||3.02|
|Wheat, hard, of Africa||64.57||19.50||7.60||2.12||3.50||2.71|
|Wheat, hard, of Taganrog||63.30||20.00||8||2.25||3.60||2.85|
|Wheat, demi-hard, of Brie (France)||68.65||16.25||7||1.95||3.40||2.75|
|Wheat, white tuzelle||75.31||11.20||6.05||1.87||3||2.12|
 The proportions of azotized substances have been deduced from the elementary analysis by multiplying by 6.5 the weight of azote obtained.]
Of the proximate or organic constituents of grasses, starch and sugar are found in large proportion, the former in the seed, the latter in the stem. These constituents, with proteinaceous matter (gluten, albumen), to which may be added gum, confer on corn its valuable nutritive properties. (For the per centage proportion of starch and proteinaceous matter in corn, see ante, p. 106, and vol. i. p. 119.)
Fragrant volatile oils are obtained from herbaceous parts of some grasses. Several of these are employed in perfumery and in medicine (see the genus Andropogon).
The grasses are remarkable for their deficiency of pectin, as well as of pectic, tartaric, citric, and other vegetable acids commonly found in plants.
Considered with regard to their dietetical uses, the grasses are most important and valuable to man. They contain nitrogenized principles fitted for the production of the essential constituents of the blood and of the organized tissues, and also non-nitrogenized principles for the production of fatty matters, lactic acid, and, by combustion, of heat. The following table gives a general view of the uses which several constituents of grains of corn serve in the animal economy:—
|1. Complex nitrogenized substances.||Gluten
|Fibrine, albumen, haematin, gelatine, chondrine, kreatin, kreatinin, inosinic acid.||Urea, uric acid, hippuric acid, kreatin, kreatinin, horny matter (in hair, nails and epidermis).|
|2. Complex non-nitrogenized substances.||Starch
|3. Mineral substances.||Poth, soda, lime, magnesia, iron, phosphoric acid, sulphur (in gluten, &c.), (fluor?), chlorine, silica.||Poth, soda, lime, magnesia, iron, phosphoric acid, sulphur (in fibrine, albumen &c.), (fluor?), chlorine, silica?||Poth, soda, lime, magnesia, iron, phosphoric acid, sulphur (in fibrine, albumen, gelatine, &c.), fluor, chlorine, silica.||Poth, soda, lime, magnesia, iron, phosphoric acid, sulphur, sulphuric acid, chlorine, fluorine, silica.|
Almost every species of grass is wholesome. Some supposed exceptions to this statement have been already noticed (see vol. i. pp. 134 and 135). Of these, the best established is Lolium temulentum, which will be presently noticed. In a state of disease, corn sometimes acquires more important and valuable medicinal properties (see Ergot.)