Rootstock shortly creeping, branches extra-vaginal and above ground, shoots rough. Blade narrow, harsh, with an acute point, thin, shining below, ridgeless, with flanking lines and keel. Ligule acute, and short or long (Fig. [8]).
Sesleria cærulea, Ard. (Blue Moor-grass), of our northern limestone hills, has narrow, flat, glaucous blue, stiff, mucronate leaves, with scabrid apex. Ligule ciliate.
Poa trivialis is most likely to be confounded with other Poas, especially P. annua and P. pratensis, since they both have thin leaves and flat shoots; but P. annua has a split sheath, less acute and duller leaves, is annual, and less harsh, and the shoot-section is flatter at the sides and rounder at the ends.
Poa pratensis, L. is larger and more stoloniferous, with both extra- and intra-vaginal branches, culms erect and smooth, sheaths smooth, and the shoot-sections elliptical—not cornered or rhomboidal—and with darker green and larger, thicker, 7-veined, more glossy, and less harsh leaves, with shorter, blunter ligule.
Poa compressa, L. also presents difficulties, but the sheath is split, and the ligule is shorter than in P. trivialis, the leaves thicker, and the shoot-sections more linear-oblong or elliptical.
(β) Sections of sheathed leaves rounded, circular or oval, there being no prominent keels.
(1) Section of sheathed leaves circular or nearly so, the shoots being only slightly compressed.
✲ Perennial.
Bromus inermis (Awnless Brome).
Sections circular, the leaves being convolute, base shelving. Glabrous sheaths and leaves. Stoloniferous. Ligule short, truncate, and finely toothed. A forage grass of the Hungarian steppes. Now being grown in this country, but of doubtful value here.
Bromus erectus, Huds. (Upright Brome). A weed.
Sections oval and rounded, but leaves equitant. Radical leaves remain folded and almost subulate, hairy edges. No stolons. Fields, &c. It is a weed on dry lands, and of little or no value.