CHAPTER VII.. Grasses Grouped According to Their Flowers and Inflorescences.

GRASSES GROUPED ACCORDING TO THEIR FLOWERS AND INFLORESCENCES.

I. GRASSES WITH ONLY ONE PERFECT FLOWER IN THE SPIKELET.

+(1) Inflorescence spikate.+

+A. Inflorescence a spike of simple spikelets.+

Nardus stricta, L. A tough wiry tufted moor-grass, with setaceous leaves, secund spikelets with a single rudimentary glume, and a stiff simple hairy style. (Fig. 2.)

The much rarer Mibora verna about three inches or so high, and Lepturus, both with flat leaves, also come here.

Certain superficial resemblances in the habit or inflorescence in Festuca Myurus and rare forms like Spartina, may occasionally cause hesitation until the spikelets are examined.

+B. Spike with sessile or sub-sessile tufts of three or more spikelets.+

(a) A spike of tufted awned spikelets, in triplets at each notch of the rachis, and one or two of each triplet barren.

+Hordeum.+

No other genus of our grasses is like Hordeum. The purely superficial resemblances in the inflorescences of Polypogon, Lagurus, and Cynosurus echinatus--all extremely rare species--disappear at once on examination.

In Bromus erectus the equally superficial resemblance is due to the stiff awns: the spikelet has six to twelve flowers and is stalked.

It should also be noted that Hordeum sylvaticum occasionally has a rudimentary second flower in the lateral spikelets (see note p. 105).

(α) A shade-grass with the central spikelet only imperfect; staminate, or rudimentary, or entirely wanting.

H. sylvaticum, Huds.

(β) The central spikelet is the perfect one, the two lateral barren. Growing in open land.

(i) A perennial meadow-grass. All the glumes scabrid and bristle-like.

H. pratense, Huds.

(ii) Annuals with some of the glumes at least, lanceolate or broad below.

* Ruderal plant, with cylindrical spikes, long awns; glumes of the central flower dilated below.

H. murinum, With.

** Maritime plant, more or less glaucous, with short ovoid spikes: glumes of the central flower bristle-like.

H. maritimum, With.

(b) Spike cylindrical, of sessile or nearly sessile awned spikelets, densely crowded round the axis, the whole resembling a fox’s brush or cat’s tail.

Species of Lagurus, Polypogon, Phalaris (not truly awned), Panicum (with bristles between the spikelets), and Gastridium are other British grasses approaching this type of inflorescence: they are all rare or very local.

Sesleria has an ovoid spike, but the spikelets are two-flowered and not truly awned.

Kœleria may present resemblances, but the spikelets are very different in detail (see p. 109).

(i) Awns inserted into the back of the single palea, and hair-like. Glumes connate below, keeled. Only one palea.

+Alopecurus.+

* Annual corn-weed, with a long and slender spike, pointed above. Glumes almost glabrous, and connate to the middle.

A. agrestis, L.

** Perennials, with shorter and stouter spikes, rounded above. Glumes connate at the base only, and obviously hairy on the keel.

† Procumbent and kneed at the nodes below. Spike 1-2 inches long. In marshy places.

A. geniculatus, L.

†† A meadow-grass, with erect stems, and spikes 2-3 inches or more and stouter.

A. pratensis, L.

The rare A. alpinus, Sm. with short ovoid spikes, about one inch long, only occurs in the Highlands.

(ii) Awns, when present, merely the stiff, pointed termination of the keel. Glumes free below. Paleæ two.

* A glaucous shore plant with long creeping stolons (sand-binder). Inflorescence harsh, 5--6 inches long. Glumes tapering, simply acute.

Psamma arenaria, Beauv.

Elymus, a much rarer sand-binder of similar habit, may lead to confusion until the 3--4 flowered spikelets and different arrangement are observed. (See p. 108.)

Agropyrum repens (var. junceum) is similar in habit and station, but its spikes and spikelets are very different (see p. 107).

Phleum arenarium is much smaller (see below).

** Erect. Inflorescence rarely longer than three inches. Spikelets flat: glumes keeled, the keel suddenly produced into a sharp stiff awn or mucronate point. Paleæ two.

+Phleum.+

† Tall perennial meadow-grass. Awn bristle-like, almost as long as the nearly glabrous glume: spike long, cylindrical.

P. pratense, L.

†† Small, compact annual shore plant, with the glumes acute only and the keel ciliate above. Inflorescence not more than 1--1-1/4 inch long.

P. arenarium, L.

The rare P. Bœhmeri, Schrad. has the glumes merely tapering to a sharp point; and the rare P. alpinum, L. has a much shorter spike and glumes ciliate on the keels.

The rare P. asperum, Jacq. has broad, shortly mucronate glumes and a longer and more slender spike.

+(2) Inflorescence a panicle--i.e. tufts or spreading stalked groups of spikelets are arranged on the main axis.+

+A. Inflorescence compact and irregular; a spike of tufts (spike-like panicle). Glumes four, the inner pair awned: paleæ minute. Stamens two only.+

Anthoxanthum odoratum, L.

The four glumes and two stamens distinguish this grass at once. Other grasses with occasionally tuft-like inflorescences--e.g. species of Agrostis, Gastridium, Aira, Dactylis, Cynosurus, Poa, Triodia, Kœleria--are distinguished at once by having three stamens (Bromus occasionally has but two), only two glumes, several flowered spikelets, &c.

+B. Inflorescence a distinctly branched panicle, more or less loose and spreading.+

(a) Tall reed-like perennials, growing in water or in marshes, with plume-like inflorescences, and silky hairs at the base of the paleæ. Glumes with a keel and point, but not awned.

(i) Spikelets purplish: outer palea with a slender dorsal awn: basal hairs longer than the paleæ. Leaves narrow. Not common.

Calamagrostis Epigeios, Roth.

(ii) Spikelets greenish. No awns: basal hairs much shorter than the paleæ. Leaves broad. Common.

Digraphis arundinacea, Trin.

A variety of Digraphis with white stripes in the leaves is grown in gardens. Other aquatic reed-like grasses are Arundo and Glyceria aquatica: both have several flowers in the spikelet.

The rare Calamagrostis lanceolata, Roth., C. stricta, Nutt. and C. strigosa, Hartm. also come here.

(b) Slender grasses, not reed-like, with delicate loosely spreading panicles of small spikelets.

(i) A tall, slender shade-grass, in woods. Paleæ very smooth and glistening. Spikelets few, distant and turgid, awnless.

Milium effusum, L.

Melica uniflora, also a wood-grass, has the spikelets two-flowered, though the upper one may be a mere rudiment, and much fewer, on a flexuous nodding axis. The much rarer M. nutans has two perfect flowers in the spikelet (see p. 105).

(ii) Grasses of open situations, with numerous small pointed spikelets. Inner palea minute or absent.

+Agrostis.+

The genus most likely to give trouble here is Aira, which though normally with two flowers in the spikelet, occasionally has but one. As regards the common species of similar habit, &c., Aira has bristle-like leaves and Agrostis flat ones.

Again, Agrostis alba has no protruding awn, as in the spikelets of Aira. For Aira cæspitosa and other details, see p. 117.

* Awnless, or at most a short bristle not equalling the palea. Leaves flat and short.

A. alba, L.

An exceedingly variable plant. The variety A. stolonifera has a less spreading panicle, and broader leaves with a long serrated and pointed ligule: the variety A. vulgaris has a spreading loose panicle, narrower leaves, and a short truncated ligule. There is, however, much difficulty in distinguishing the intermediate forms on mountain-pastures, &c.

** Distinctly awned. Leaves narrower, the lower ones inrolled and almost setaceous.

A. canina, L.

The rarer A. setacea, Curt. with subulate leaves and A. Spicaenti, L. with long awns also come here.

The lax spreading type of panicle characteristic of Aira and Agrostis, &c., described above, occurs in species of Avena, Bromus, Briza, Poa and Catabrosa, but the basal silky hairs and twisted awns (Avena), long sub-terminal bristle-awns (Bromus), habit (Catabrosa), and the presence of two, three, or more flowers in the considerably larger spikelets of all, easily distinguish them.

The rare grasses Leersia, with two glumes and no paleæ, and Gastridium, with curiously bullate bases to the glumes, also come into this group with one-flowered spikelets, but their characters must be studied with the flora. The same remark applies to species of Panicum, Cynodon, Spartina and other aliens, occasionally met with.

II. GRASSES WITH AT LEAST TWO FLOWERS--OF WHICH ONE MAY BE IMPERFECT--IN THE SPIKELET.

+A. Only one perfect flower, the other staminate only or altogether rudimentary. Inflorescence a loose or racemous panicle.+

In Hordeum sylvaticum the two lateral spikelets occasionally conform to this heading (see p. 100), and the same is said to be the case sometimes in Aira (see p. 104). The rudiments are extremely minute, however, and hardly suffice to justify the removal of these grasses to this group.

In one or two species of Aira the panicle may be somewhat contracted and tuft-like.

The very rare Hierochloe has one perfect flower, and two lower staminate ones in each spikelet.

(a) A shade-grass found in woods. Awnless. One flower perfect, the other (upper) reduced to a small stalked knob. Inflorescence racemous.

Melica uniflora, L.

The much rarer M. nutans has two perfect flowers and a similar rudiment (see note, p. 104).

(b) Grasses of open situations, spikelets with awns. The reduced flower staminate.

* Upper flower perfect, lower staminate only. Tall oat-like meadow-grass, with a bent and twisted dorsal awn to the outer palea of the lower flower: silky hairs at the base of paleæ.

Arrhenatherum avenaceum, Beauv.

The grasses most like this are species of Avena and Aira. The former have two or more perfect flowers, and the only broad-leafed Aira--A. cæspitosa, see p. 117--is easily distinguished by its leaves and its very small spikelets and short simple awns.

** Upper flower staminate: lower perfect. Small hairy grasses, with red-veined basal leaf-sheaths and short simple awns.

+Holcus.+

† Erect, evenly hairy, glumes blunt, awn not protruding. Common.

H. lanatus, L.

††, More or less procumbent, hairs chiefly at the nodes. Glumes pointed. Awns simple and exserted. Rarer.

H. mollis, L.

+B. Each spikelet with at least two perfect flowers, often more.+

(+1+) +Inflorescence spikate, the main axis bearing sessile or sub-sessile spikelets, each containing three or more flowers.+

(a) Spike simple, axis stout and notched, each notch having one spikelet closely sessile in it.

(i) Spikelets distichous, the flat side of each--i.e. the edges of the glumes--being next the axis (rachis).

+Agropyrum.+

* A weed with creeping stolons, and no awns or mere points to the glumes.

A. repens, Beauv.

The variety A. junceum found as a sand-binder on sea-coasts is glaucous, stiffer, with sharply pointed leaves, and blunt glumes. For other sand-binders see note, p. 102.

** Not creeping. Awns long and prominent.

A. caninum, Beauv.

(ii) The rounded backs of the glumes are next the rachis.

* Spikelets flat and closely sessile in the notches of the rachis.

+Lolium.+

† Awnless or nearly so. Perennial.

L. perenne, L.

†† With conspicuous awns. Annual, not common.

L. temulentum, L.

There are several cultivated varieties of L. perenne: L. temulentum is notoriously poisonous (see note, p. 168). The lowermost glume of each spikelet is often alone developed or conspicuous, and looks like a bract in the axis of which the spikelet sits.

** Spikelets elongated and hardly flattened, and not quite sessile, especially the lower: rachis scarcely notched, the spikelets with their sides (edges of glumes) next the axis.

+Brachypodium.+

† A shade-grass with long, conspicuous awns to the more or less drooping spikelets. Common.

B. sylvaticum, Beauv.

†† Growing in the open. Spikelets stouter, stiffer and more erect, with short awns. Not common.

B. pinnatum, L.

Brachypodium may easily be confounded with Bromus, but the spikelets are nearly sessile: their shape and the absence of conspicuous notches distinguish this genus from Agropyrum. Lolium has a conspicuously notched rachis and the spikelets arranged in the other plane.

Poa loliacea, Huds., an uncommon sea-shore weed, may also be placed here; as also Festuca elatior, var. loliacea, Curt. and some forms of Bromus arvensis, var. mollis, L.

No other British grasses resemble Brachypodium: any superficial likeness remarked in species of Hordeum, Festuca, &c. disappears at once on examination.

(b) Spike compound--i.e. with clusters of two or more sessile or sub-sessile spikelets arranged along the rachis.

(i) Spike elongated, fertile spikelets with 3-5 flowers.

* Pasture-grass with wiry rachis, on which the spikelets are secund and sessile in clusters: in each cluster a comb-like group of barren glumes subtends one of fertile spikelets.

Cynosurus cristatus, L.

The rare C. echinatus has the pectinate groups of barren glumes even more prominent.

** Stout glaucous sand-binder with pairs of spikelets sessile in the notches of the rachis, and all fertile. Spike cylindrical. Not common.

Elymus arenarius, L.

For other sand-binders see p. 102. The only grass likely to be confounded is Agropyrum, in which the spikelets are not paired. Lolium, Brachypodium, &c. are easily distinguished.

(ii) Spike short and ovoid: spikelets sub-sessile and imbricate, in clusters. Bluish.

Sesleria cærulea, Ard.

Not easily mistaken for any other grass. As some of the spikelets are shortly stalked, the inflorescence is strictly paniculate, but the fact is not obvious. The glume-like bract at the base of the spike, and the general appearance suggest resemblances to certain moor-sedges at first sight. The only other grasses with similarly shaped spikes are species of Alopecurus, Phleum, and the rare Lagurus, Polypogon, Phalaris, Panicum, all with very different spikelets and easily distinguished.

(+2+) +Inflorescence a panicle or raceme--i.e. the spikelets on evident stalks, simple or branched, from the main axis.+

It does not follow that every spikelet is distinctly stalked, and cases occur where the stalks are very short and stiff: when this happens to the stalks arising from the main axis, and the latter is elongated, the type of the spike is closely approached, and the inflorescence resembles that of Brachypodium, Lolium, &c. In some depauperated varieties of Poa, Festuca, &c., an actual spike results (see note, p. 111): the number of flowers in the spikelet is important.

a) Panicle short, contracted and tuft-like, owing to the shortness and stiffness of most of the stalks and their tendency to remain erect, at least until anthesis. Glumes keeled and ending in a point.

(i) Panicle with a few branches, at first erect, ending in tuft-like secund clusters. Spikelets harsh, with 3-5 flowers. Coarse meadow-grass.

Dactylis glomerata, L.

Not easily confounded with any other grass if attention is paid to the folded coarse leaves, the tufted perennial habit, and the harsh inflorescence, the glumes on the spikelets being stiffly hairy on the keel.

(ii) Panicle contracted, more or less ovoid or cylindroid, but most of the spikelets stalked, and not aggregated into dense clusters, spikelets silvery, containing 2-3 flowers.

Kœleria cristata, Pers.

Any resemblances to forms of Aira are at once nullified by the absence of true awns in Kœleria. Festuca and Poa have more numerous flowers in the spikelet. Anthoxanthum has only one flower, with two stamens, in the spikelets. Phleum and Alopecurus present resemblances, but see pp. 101 and 102.

(b) Panicle elongated and lax--i.e. all or most of the spikelets on distinct slender stalks, longer than themselves.

(i) Panicle close: the spikelets on distinct and even long stalks, but the latter erect and keeping the spikelets near the main axis.

In some cases the stalks from the main axis bear only one spikelet each and the type of inflorescence is that of a raceme; usually, however, one or more of the lowermost stalks branch and disclose the panicle.

* Panicle with few simple branches, racemous, each spikelet large and containing about four flowers, palea three-toothed at the apex. A small heath-grass, with hairs at the ligule.

Triodia decumbens, Beauv.

The inflorescence may have some resemblance to Melica (see p. 105), but the four-flowered spikelet, ligule, habitat and stature distinguish it at once.

** Panicle with divided branches, which are more or less erect.

† Spikelets awnless.

⊙ Spikelets small, purplish, with two or at most three florets; the upper on a stalk. Coarse moor-grass.

Molinia cærulea, Mœnch.

⊙⊙ Spikelets with six or more florets.

‡ Tall aquatic grass with long, lax, narrow panicle and spikelets, somewhat nodding, and with 8-20 flowers in each.

Glyceria fluitans, Br.

The only similar grass is Glyceria aquatica, Sm. which differs in its more reed-like habit, open panicle, and fewer flowers.

‡‡ Small land-plants not more than a foot high, with short, stiff, somewhat crowded panicles, and spikelets containing 6-8 flowers.

≡ Maritime perennial with creeping stolons, and about a foot high: panicle somewhat open below.

Poa maritima, Huds.

≡≡ Inland plant with secund panicle, about six inches high.

P. rigida, L.

The rare P. procumbens, Curt. and P. bulbosa, L. also come here, as well as starved forms of P. compressa, L. Some forms of Festuca elatior, var. pratensis, Huds. growing in dry situations may give trouble, and will have to be examined with the flora. See also note, p. 109.

†† Spikelets awned.

⊙ Awns bristle-like and terminal on the paleæ: flowers about six in each spikelet. Leaves setaceous. Panicle secund.

≡ Awns long and bristle-like. An annual weed.

Festuca Myurus, L.

≡≡ Awns very short, or merely the drawn out points of the paleæ. Perennial.

F. ovina.

The rare F. uniglumis, Soland., and some other varieties may also come here.

Some forms of F. ovina are viviparous (see p. 134), and several varieties have to be distinguished.

⊙⊙ Awns hair-like and dorsal on the paleæ. Flowers two in each spikelet. Annual, six inches or less in height.

Aira præcox, L.

The rare A. canescens, L. also comes here: its awn is jointed and with a minute tuft of hairs about the middle.

(ii) Panicle lax and open, the fine hair-like branches spreading widely during florescence, or even pendent or drooping.

* Spikelets awnless.

† A small aquatic grass with prostrate habit and two-flowered spikelets with broad truncate glumes and paleæ.

Catabrosa aquatica, Beauv. (Fig. 4).

The two-flowered spikelets distinguish it at once from Glyceria aquatica, to say nothing of its softer and smoother texture and small stature. Poa trivialis may have two flowers, but it is an erect meadow-grass, with keeled and pointed glumes and paleæ. Aira and Agrostis are awned, or differ entirely in habit.

†† Spikelets with at least three or four, but usually more flowers.

⊙ A perennial field-grass with few large, compressed, bluntly triangular or ovate spikelets, dangling at the end of capillary branchlets; with membranous, loosely imbricated, concave and inflated paleæ and glumes, and 6-8 flowers.

Briza media, L.

The much rarer B. minor, L. is an annual and smaller.

⊙⊙ Spikelets small and numerous, more or less elongated and pointed, not dangling: glumes and paleæ not inflated.

Poa and Festuca (see p. 116) are difficult genera for the beginner; several of the species vary considerably in detail. Generally speaking the spikelets of Festuca are hard, harsh and sharply pointed, or with short or evident awns; in Poa they are softer, and with blunter points, and never awned. The most obviously awned species of Festuca have more or less setaceous leaves and contracted inflorescences (see p. 111). Some of the mountain species of Poa are extremely variable in small characters.

≡ Reed-like aquatic, with obtuse glumes rounded dorsally; the large richly branched panicle bearing numerous 5-10 flowered spikelets. Sheath entire or nearly so. No we to the paleæ.

Glyceria aquatica, Sm.

For other reed-grasses, see note, p. 103. Glyceria fluitans has a more contracted panicle and usually more flowers in the spikelet &c. (see p. 111).

≡≡ Meadow and pasture grasses &c., usually small. Glumes more or less keeled and acute. Sheaths split.

+Poa.+

‡ Spikelets very small and containing 2-3 flowers only. Stem slender, terete and rough; ligule long and acute, palea with prominent lateral nerves.

P. trivialis, L.

The flowers are fewer than in any other Poa, and may be only two. P. nemoralis, with 3-5 flowers, may also occasionally be found with two only: it differs from others in its more acute glumes, smooth stem and short ligule.

P. pratensis differs in its creeping stolons, short ligule and more numerous 4-5 flowers, and in the indistinct nerves of the palea.

‡‡ Spikelets 4-6 flowered.

≡ Annuals, about six inches high, with relatively large and numerous spikelets for so small a panicle. No “web” at the base of the paleæ.

P. annua, L.

This is the small grass so common as a weed on road-sides and on lawns, flowering even in winter. For other annual species of Poa--P. rigida, P. loliacea and P. procumbens--see note p. 108 and p. 111.

≡≡ Perennials.

Δ With creeping stolons.

x Stems and leaf-sheaths flattened. Panicle somewhat close and secund, some spikelets being nearly sessile.

P. compressa, L.

xx Stems and leaf-sheaths terete. Panicle spreading widely.

P. pratensis, L.

ΔΔ Without creeping stolons. Stems and panicle slender, round. A shade-plant.

P. nemoralis, L.

The rarer species of Poa are P. bulbosa with the stems swollen below; P. alpina, also slightly bulbous and often viviparous; P. laxa an allied Highland species; and P. distans a maritime form allied to P. maritima (see p. 111).

** Spikelets with awns or with sharp terminal points (awn-points) to the glumes or paleæ.

In some species and varieties of Festuca awns are not evident (see p. 116): the hard paleæ simply end in acute or acuminate points, but these are sharp and in most cases much more so than in any Poa. When not so evident, the student will probably think the specimen is a Poa and the flora must be consulted.

The difficulty is most likely to occur with varieties of F. ovina and F. elatior: in the former the leaves are narrower, setaceous and stiffer than in any Poa. The ribbing of the leaf, the ligule, and other characters of the vegetative organs (see pp. 45 and 50) will help in these doubtful cases.

† Awns terminal, or sub-terminal; often very short or nearly obsolete and the paleæ merely drawn out at the tips to a hard sharp awn-point.

⊙ Awns long and sub-terminal, inserted between the teeth of the cleft apex of the paleæ. Sheaths entire. Panicle usually nodding.

+Bromus.+

With the exception of Festuca Myurus and one or two other rare Fescues with setaceous leaves, Hordeum and Brachypodium are the only other genera with awns much resembling the Bromes. The former has a totally different inflorescence, and in the latter the spikelets are practically sessile (see p. 107).

≡ Spikelets short and fat, and relatively heavy. Paleæ broad and distinctly nerved. Awns fine, about as long as the paleæ.

B. arvensis, L.

There are several varieties, of which B. secalinus with a looser panicle, and B. mollis with a more compact panicle and very downy, are the chief.

≡≡ Spikelets lanceolate and with conspicuous awns. Nerves on the paleæ obsolete.

x Panicle conspicuously loose and drooping and awns long, paleæ narrow and elongated.

z Sheaths with long often reflexed hairs. A shade-grass over three feet high.

B. asper, Mull.

zz Sheaths downy. A weed of open lands and hedges, two feet or less.

B. sterilis, L.

B. giganteus is rarer than B. asper and has smaller spikelets and more slender awns. B. maximus and B. madritensis are rare.

⊙⊙ Awns, if present, merely the points of the paleæ, very short or obsolete. Sheaths split: ligule short.

+Festuca.+

≡ Leaves flattened. Panicle somewhat close. Often tall grasses.

z Meadow-grass, with 5-6 to a dozen or more flowers in the spikelet.

F. elatior, L.

zz Shade-grass, with 4-5 flowers only in the spikelet.

F. sylvatica, Vill.

≡≡ Leaves subulate or setaceous, at least below. Mountain pasture grass, usually small.

F. ovina.

Concerning difficulties between Poa and the awnless forms of Festuca, see p. 114. F. elatior and F. sylvatica are practically awnless, the awn-points being merely the acuminate tips of the paleæ.

The long-awned species of Festuca have compact stiff panicles and narrow or setaceous leaves (see p. 111).

Regarding varieties of F. ovina, see p. 112.

†† Awns, twisted below and bent above, inserted into the middle of the back of the bifid palea or below it.

⊙ Awns long and conspicuously projecting from the spikelet, which is gaping and contains 3-5 flowers. Leaves flat.

+Avena.+

≡ Tall annual corn-weed, with large (18-20 mm.) heavy, pendent, hairy spikelets on the long slender stalks of the lax open panicle. Leaves glabrous.

A. fatua, L.

This is the so-called Wild Oat, and the type of this group.

≡≡ Tufted perennials with spikelets more or less erect on stiffer stalks, the panicle therefore less open.

z Panicle nearly simple; spikelets silvery or reddish, 12-15 mm. long.

A. pratensis, L.

zz Panicle branched but not very open; spikelets glistening yellow and only 5-6 mm. long.

A. flavescens, L.

There is no other genus closely resembling Avena. The superficial likeness of some Bromes disappears at once on examination. The spikelets of Aira are much smaller, and the leaves quite different (see below and p. 47).

⊙⊙ Awns fine and hair-like and not conspicuously protruding from the spikelets; the latter small, 2-5 mm. Flowers two in each spikelet.

+Aira.+

≡ Coarse and tall tufted grass with flattened, harsh, and conspicuously ribbed leaves: the very short awns hardly protruding.

A. cæspitosa, L.

No other grass can be confused with this if the very high ridges of the leaves are observed (see p. 47).

≡≡ Small grasses with setaceous or very narrow inrolled leaves. Awns slightly protruding.

x Palea distinctly bifid at the apex: awn nearly twice its length. A very small grass about six inches high: leaves subulate, fine and short.

A. caryophyllea, L.

xx Paleæ almost imperceptibly bidentate: awn not much longer than palea. About 12-18 inches high: leaves inrolled.

A. flexuosa, L.

Other species of Aira, with more condensed inflorescences, are dealt with on p. 112. Agrostis is distinguished by the leaves and one-flowered spikelets (see p. 104). Poa and Catabrosa have no awns.