Lolium perenne presents some difficulties in relation to such forms as L. italicum, species of Agrostis and Festuca, Alopecurus pratensis, Cynosurus and Agropyrum.
Owing to the leaves not being always strictly conduplicate in the first year, the flat shoots may not sharply mark it off from L. italicum. Its somewhat looser, almost stoloniferous tufts, and darker green foliage, less polished below and usually narrower and harder, have then to be taken into account.
The ridges of Lolium are often like those of Festuca pratensis; and the shining lower surface and rather firm leaves and red sheaths, present other points of confusion. The smooth basal margins of Lolium, absence of white translucent lines when held up, and the different ligule and ears afford distinctions—the ligule of Festuca being a mere line, and the ears pointed and projecting, whereas they may be mere lateral ledges in Lolium.
Cynosurus has the ligule and ears very like those of Lolium, the ears being mere ledges; but the former has yellow sheaths, firmer and thicker leaves with more evident ridges, and the old plants usually have the characteristic crested spikes remaining. Cynosurus, moreover, has the sheath split only a short way down.
With regard to Agrostis, there is no colour in the sheath, the ligule is longer and pointed, and the leaves drier and thinner than in Lolium, and harsher on both surfaces. Agrostis has also no ears.
Alopecurus pratensis has much broader and flatter ridges than Lolium and a longer ligule, and its sheaths are dark-brown or black—not red; but A. agrestis has very similar ridges to Lolium and may easily be confounded at first.
Agropyrum is sometimes nearly glabrous, and may then be confused with Lolium by beginners: its low ridges, curled and pointed ears, obsolete ligule, and thinner, drier, harsher blade, as well as the stolons, distinguish it.
Lolium temulentum and Hordeum murinum occasionally cause difficulty, but the latter is always more or less hairy, its blades thinner and drier, and the ridges less raised.
†† Sections rounded—elliptical or nearly circular. Sheath distinctly split, at least above.
Cynosurus cristatus, L. (Crested Dog’s-tail). Useful as pasture on dry soils, but only moderately so as hay. Blade narrow, slightly eared or collared below, tapered above; firmer than Lolium. Sheath only split a short way down. Yellow or yellowish-white at the base. Leaves conduplicate or convolute, short and narrow, the ligule short: minute ears at base. Usually easily recognised by the withered culms and persistent pectinate spikes (Fig. [15]).
Festuca elatior, L. (Meadow Fescue). A valuable meadow and pasture grass, though somewhat coarse. Several varieties are known. Best on heavy soils. Deep rooted. Blade flat and broad, conduplicate, sharp-eared at the base, and there rough at the margin: lower surface polished. Rich green. Mid-rib flat above, numerous ribs with white lines between if held up and examined with a lens. Ligule obsolete (Figs. 12 and 17).
Arundo Phragmites, L. (Common Reed). A large aquatic, reed-like creeping grass, with broad leaves (3/4 to 1 in.), flat, rather rigid, acuminate, glaucous below, hispid at edges. Sheath smooth, striate, bearded at mouth. Ligule a mere fringe of hair. (Cf. Digraphis, p. [54.])
Cynosurus is not very liable to confusion; but it has resemblances to Lolium (see p. [49]) and to species of Agrostis. The leaves of Cynosurus are firmer, thicker, less dry, and with a shining undersurface, and the sheath is only split above, and yellow below; whereas Agrostis has relatively thin and dry leaves, rough surfaces and margin, distinct ridges, and converging margins as the blade nears the sheath.
Festuca elatior is easily confused with the glabrous Bromes. For B. giganteus see p. [43].
Bromus erectus is distinguished by the entire sheath, usually hairy, the want of auricles, and the conduplicate—not convolute—leaves.
Agrostis has thinner, duller, and drier leaves, and no red sheath.
Alopecurus pratensis has more depressed, flatter and broader ridges than Festuca, and a longer ligule, and lacks the pointed ears.
✲✲ Ligule whitish, membranous, long, or at least well developed. Sheaths not coloured or brown. Leaves thin and rough, at least at the base. Ridges not very prominent, but numerous and distinct.
Agrostis stolonifera, L. (Fiorin). Stolons, with numerous short offsets bursting through the leaf-sheaths. Blade flat, rough, tapering, with rounded ridges, and convolute in bud: there are no auricles, but the blade may narrow, and form ledges, as it runs into the sheath. Sheaths nearly smooth. Ligule long and pointed, and often toothed at the margins. The leaves vary in breadth.
This and A. vulgaris, With. with shorter ligules, and, possibly, A. canina, L. with finer leaves, are varieties of A. alba, L. Only the variety A. stolonifera is of moderate value for pasture, especially on poor soils, as it lasts late into autumn: the others are weeds, like couch-grass.
Agrostis is full of difficulties for the beginner. The weed-forms often spring up after wheat has been cut, and count as “twitch," like Agropyrum.
All the ordinary forms—A. stolonifera, A. vulgaris, and A. canina—may be included in A. alba (Linn.). On dry hills a close tufted grass, with setaceous leaves, and in rich soils creeping and luxuriant with broad leaves. It is one of the few grasses that thrive in wet soils.
The chief points in the flat-leafed forms are the thin, dry leaves, rough on both sides and on the margins, with distinct raised ridges, and the base of the leaf narrowing suddenly into its insertion with the sheath, with no auricle, but with a long membranous ligule. The sheath not coloured, and the blade convolute.
Again, A. stolonifera has a long, serrated, acute ligule, while A. vulgaris has a much shorter, entire and truncate one, and narrower leaves.
Agropyrum is the grass most likely to lead to confusion. Its ears, lower ridges, very short or obsolete ligule, and pubescence (sometimes glabrous) distinguish it.
Cynosurus sometimes gives trouble (see p. [50]) with Alopecurus pratensis: the sheaths, ligule and flattened ridges should suffice for distinction.
Alopecurus geniculatus is even more like Agrostis, but its ridges are more prominent and sharp, and its aquatic habit and bent "knees" distinguish it.
Alopecurus agrestis, in dry corn-fields, has a thickened ligule, sometimes coloured, and is annual or biennial, but otherwise very like Agrostis.
Alopecurus pratensis, L. (Meadow Foxtail). Large grass with stolons; very early, and much prized as pasture and hay, but soon dies out on light poor soils. Especially good for stiff soils. Sheaths long, ridged, brown or nearly black at the base as they age. Ligule distinct and obtuse, entire. Leaves numerous. Blades long, dark green, succulent and scabrous: ridges numerous and flat above, but distinct (Fig. [9]).