Almost the only plants confounded with true grasses by the ordinary observer are the sedges and a few rushes. Apart from the very different floral structures, there are two or three easily discoverable marks for distinguishing all our grasses from other plants (Fig. 1). The first is their leaves are arranged in _two rows_, alternately, up the stems; and the second that their stems are circular or flattened in section, or if of some other shape they are _never triangular_ and _solid_[1] (Figs. 6 and 7). Moreover the leaves are always of some elongated shape, and without leaf-stalks[2], but pass below into a _sheath_, which runs some way down the stem and is nearly always perceptibly split (Figs. 8-13). Further, the stems themselves are usually terete, and distinctly hollow except at the swollen nodes, and only branch low down at the surface of the ground or below it[3]. [Illustration: Fig. 1. A plant of Oat (_Avena_), an example of a typical grass, showing tufted habit and loose paniculate inflorescence (reduced). Figuier.] All our native grasses are herbaceous, and none of them attain very large dimensions. In the following lists I term those small which average about 6-18 inches in the height of the tufts, whereas those over 3 feet high may be termed large, the tufts being regarded as in flower. The sizes cannot be given very accurately, and starved specimens are frequently found dwarfed, but in most cases these averages are not far wrong for the species freely growing as ordinarily met with, and in some cases are useful. I have omitted the rare species throughout, and in the annexed lists have added the popular names. LARGE GRASSES. (Over 3 feet.) _Milium effusum_ (Millet-grass). _Digraphis arundinacea_ (Reed-grass). _Aira cæspitosa_ (Tufted Hair-grass). _Arrhenatherum avenaceum_ (False Oat). _Elymus arenarius_ (Lyme-grass). _Bromus asper_ (Hairy Brome). _B. giganteus_ (Tall Brome). _Festuca elatior_ (Meadow Fescue). _F. sylvatica_ (Reed Fescue). _Glyceria aquatica_ (Reed Sweet-grass). _G. fluitans_ (Floating Sweet-grass). _Arundo Phragmites_ (Common Reed). MEDIUM GRASSES. (1-3 feet.)