Annual or perennial, erect or creeping herbs, rarely (bamboos) shrubby or arborescent. Stem (culm) branched at the base, cylindrical or slightly compressed, jointed, generally hollow between the joints; joints (nodes) solid, swollen. Leaves alternate, distichous, usually long and narrow, entire, parallel-veined; sheath long, split to the base on one side, at its junction with the blade usually furnished with an erect membranous appendage called the ligule. Flowers hermaphrodite or unisexual, minute, solitary in the axils of small bracts (glumes) which are imbricated in 2 opposite rows, forming little spikes or spikelets. Spikelets usually many, arranged in spikes, panicles, or fascicles. Glumes placed alternately on each side of the axis (rhachilla) of the spikelet, the first or lowest 1–6 (commonly the first 2) empty and known as empty glumes or outer glumes, or simply as glumes. The succeeding 1 or several are called -flowering glumes, each of them having in its axil a very short branchlet bearing on its upper side a 2-nerved bractlet called the palea; the branchlet ending in a flower, which is thus enclosed by the flowering glume and palea. Occasionally 1 or more glumes at the top of the spikelet are empty or enclose rudimentary flowers only. Perianth wanting, unless represented by 2 (rarely 3) minute scales (lodicules). Stamens usually 3, rarely 1, 2, or 6, hypo-gynous; filaments capillary; anthers pendulous, versatile, fugacious. Ovary 1-celled; styles 2 or rarely 3, free or connate at the base, feathery with simple or branched stigmatic hairs; ovule solitary, erect, anatropous. Fruit a seed-like utricle or grain (caryopsis) either free within the flowering glume and palea, or adhering to one or both. Seed erect, usually adherent to the membranous pericarp, rarely separable (Sporobolus); albumen copious, farinaceous; embryo very small, roundish, on one side of the base of the albumen.

One of the largest of the families of plants, found in all climates and situations, but most numerous in temperate regions. Genera about 325; species page 839probably not less than 3500. In usefulness to man it is exceeded by no other order. The nutritious herbage forms the chief pasturage of our flocks and herds; the cereal grains, as wheat, barley, rye, oats, rice, millet, maize, &c, constitute a very large proportion of our food; sugar is obtained from the sugar-cane and sorghum; while few plants are applied to a greater variety of uses than the various kinds of bamboos. Many species are cultivated for ornamental purposes, from the dwarf varieties used for edgings and lawns to the pampas-grass and giant-bamboo. Of the 33 indigenous genera, one only (Simplicia) is endemic; 4 (Microlœna, Echinopogon, Dichelachne, and Amphibromus) are found elsewhere in Australia and Tasmania alone; and 2 others (Ehrharta and Asperella) have a vary restricted range, but are not indigenous in Australia. The remaining 26 are widely distributed in either temperate or tropical regions or in both, and some are cosmopolitan. In addition to the indigenous species, a large number of grasses have become naturalised, and every year adds to the list. Most of these are natives of the Northern Hemisphere, and many have been purposely introduced and widely spread through the country on account of their value for pasturage or fodder. The remainder are either weeds of cultivation or inhabitants of waste-places or roadsides, a large proportion having followed the footsteps of civilised man all round the world. A few Australian and subtropical species have also established themselves, but the number of these is not nearly so large as might have been anticipated. Many of the naturalised species have so completely amalgamated with the indigenous flora as to present all the appearance of true natives, and will certainly be taken as such by a beginner unacquainted with their history. It will therefore be advisable, when determining any species, to make frequent reference to the list of naturalised species given in another part of this work, and to become acquainted with their distinguishing characters, which, in the majority of cases, can be learned from any British Flora.

I am deeply indebted to Professor E. Hackel, of St. Poelten, Austria, so well known for his wide acquaintance with the order, for undertaking a critical examination of the whole of the New Zealand species, and for furnishing me with very full and complete notes, with permission to use the same for the purposes of this work. In drawing up the following account I have largely availed myself of the results of his work, and with few exceptions have adopted the systematic disposition of the species recommended by him.