This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Annual or perennial herbs, of various habit, rarely shrubs or trees. .Culms (stems) generally hollow, but occasionally solid, the nodes closed. Leaves sheathing, the sheaths usually split to the base on the side opposite the blade; a scarious or cartilaginous ring, naked or hairy, rarely wanting, called the ligule, is borne at the orifice of the sheath. Inflorescence spicate, racemose or paniculate, consisting of spikelets composed of two to many 2-ranked imbricated bracts, called scales (glumes), the two lowest in the complete spikelet always empty, one or both of these sometimes wanting. One or more of the upper scales, except sometimes the terminal ones, contains in the axil a flower, which is usually enclosed by a bract-like awnless organ called the palet, placed opposite the scale and with its back toward the axis (rachilla) of the spikelet, generally 2-keeled; sometimes the palet is present without the flower, and vice versa. Flowers perfect, pistillate, or staminate, sometimes monoecious or dioecious, subtended by 1-3 minute hyaline scales called the lodicules. Stamens 1-6, usually 3. Anthers 2-celled, versatile. Ovary i-celled, 1-ovuled. Styles 1-3, commonly 2 and lateral. Stigmas hairy or plumose. Fruit a seed-like grain (caryopsis). Endosperm starchy.
About 4500 species, widely distributed throughout the world, growing in water and on all kinds of soil. Those yielding food-grains are called cereals. The species are more numerous in tropical countries, while the number of individuals is much greater in temperate regions, often forming extended areas of turf. The time of year noted is that of ripening seed.
A. Spikelets articulated below the empty scales or a subtending involucre, or attached to and deciduous with the internodes of a readily disarticulating rachis, 1-flowered, or if 2-flowered the lower imperfect, usually staminate: rachilla not extending beyond the uppermost scale. Spikelets round or dorsally compressed; hilum punctiform.
Fruiting scale and palet hyaline, thin, much more delicate in structure than the thick-membranous to coriaceous empty scales. Spikelets unisexual, the pistillate borne in the lower, the staminate in the upper, part of the same spike. I. Maydeae.
Spikelets in pairs, one sessile, perfect, the other pedicellate, perfect, staminate or empty, sometimes reduced to a single scale or wanting. II. Andropogoneae.
Fruiting scale and palet never hyaline and thin, as firm as the empty scales, or firmer. Fruiting scale and palet membranous; spikelets naked, spiny (in ours). III. Zoysieae.
* Text contributed by Mr. George V. Nash.
Fruiting scale and palet chartaceous or coriaceous, differing in color and appearance from
the remaining scales; spikelets sometimes enclosed in an involucre.
Spikelets laterally compressed; hilum linear.
B. Spikelets articulated above the empty scales (below them in nos. 38, 41, 49, 57 and 64) which
are persistent, 1-many-flowered; rachilla sometimes extending beyond the uppermost scale.
Culms herbaceous, hence annual; leaf-blades sessile, not articulated with the sheath.
Spikelets in panicles or racemes, usually upon distinct and often long pedicels.
Empty scales 4; palets 1-nerved.
Empty scales 2 (rarely 1); palet usually 2-nerved.
Flowering scales usually shorter than empty ones, awn dorsal, bent
Flowering scales usually longer than the empty ones, awnless, or if awned the awn
terminal and straight, rarely dorsal.
Spikelets borne in 2 rows:
On one side of a continuous axis, forming 1-sided spikes or racemes.
On opposite sides of a continuous or sometimes articulated axis, forming equilateral
spikes (unilateral in Nardus).
Culms woody, perennial; leaf-blades petiolate, articulated to the sheath.
Tribe I. Maydeae.
Pistillate spikelets imbedded in the internodes of the thick rachis. 1. Tripsacum.
Tribe II. Andropogoneae.
Internodes of the rachis of the racemes thickened, appressed to the pedicels of the primary spike-lets, thus forming excavations for the reception of the secondary or sessile spikelets; fertile
flowering scales awnless.
Internodes not thickened, and without excavations for the reception of the spikelets.
Spikelets all perfect, awned.
Rachis of the racemes continuous; panicle axis short, racemes subflabellate.
Rachis articulated; panicle axis elongated.
Sessile spikelets perfect, the pedicellate staminate or empty, awnless, sometimes wanting.
Inflorescence simple or compound, made up of 1 or more spike-like racemes which are sessile or on very short peduncles.
Raceme single; pedicels and internodes of the rachis clavate, spongy, usually stout, with
a deep cup-shaped depression at the top.
Racemes not single; pedicels and rachis-internodes filiform, or flat and linear, not spongy, nor appendaged at the apex.
Racemes in pairs, or digitate in s's or less, sessile, or only 1 pedunculate; pedicels
and internodes not sulcate nor with a median hyaline line.
Racemes numerous, on an elongated axis, more or less pedunculate; pedicels and
internodes of the rachis with a median hyaline line.
Pedicellate spikelet wanting.
Pedicellate spikelet present.
Tribe III. Zoysieae.
Spikelets in a terminal spike; second scale spiny.
Tribe IV. Paniceae.
Spikelets without a subtending involucre of bristles or valves.
Spikelets all alike.
Palets not enlarged when mature.
Fruiting scale chartaceous the margins hyaline and flat.
Spikelets in slender racemes borne toward the summit of the stem,
. 11. Syntherisma.
Spikelets in an open panicle on long pedicels.
Fruiting scale indurated, rigid, the margins inrolled and not hyaline.
Opening in the fruiting scale turned toward the rachis.
Spikelets with a swollen ring-like callus at the base; fruiting scale mucronate or
Spikelets without a callus; fruiting scale not mucronate.
Opening in the fruiting scale turned away from the rachis.
Spikelets plano-convex, in secund racemes, usually of 3 scales.
Spikelets unequally bi-convex, in panicles, or rarely in secund racemes; scales 4.
Scales or some of them awned; fruiting scale cuspidate.
Second scale like the third, few-nerved not broad and saccate.
Second scale unlike the third, 11-13-nerved, broad, saccate.
Palet in the axil of the third scale much enlarged and somewhat indurated when mature,
forcing the spikelet open.
Spikelets of 2 kinds, one in terminal panicles and not producing seed, the other subterranean
and perfecting seed.
Spikelets with an involucre:
Of bristles, persistent; inflorescence a dense cylindric spike-like panicle.
Of 2 spine-bearing valves enclosing the spikelets, deciduous with them.
Tribe V. Oryzeae.
Pistillate spikelets ovate, at the base of each branch of the panicle.
Pistillate spikelets linear, on the upper branches of panicle.
Spikelets all perfect, broad, compressed; in swamps or wet grounds.
Tribe VI. Phalarideae.
Third and fourth scales
Small and empty, or rudimentary, not awned; stamens 3.
Empty, awned upon the back; stamens 2.
Subtending staminate flowers, stamens 3; fertile flowers, stamens 2.
Tribe VII. Agrostideae.
Flowering scale indurated at maturity, firmer than the empty scales.
Spikelets with no basal callus; flowering scale awnless, margins inrolled.
Spikelets with a basal callus; flowering scale awned, the margins flat.
Flowering scale broad, the awn deciduous; callus short, obtuse.
Flowering scale glabrous, or pubescent with short hairs.
Flowering scale pubescent with copious long silky hairs.
Flowering scale narrow, awn persistent; callus commonly acute.
Flowering scale membranous, not firmer than the empty scales.
Flowering scale with a terminal awn or awn-pointed, tightly enclosing the grain.
Rachilla not prolonged beyond the base of the flowering scale; empty scales usually evident.
Rachilla extending beyond the base of the flowering scale as a bristle-like appendage; empty
scales minute, the first sometimes wanting.
Flowering scale awnless, or with a dorsal awn, loosely enclosing the grain.
Spikelets readily deciduous entire at maturity.
Empty scales awnless.
Empty scales awned.
Spikelets not deciduous entire, the empty scales persistent, flowering scales usually deciduous.
Empty scales awned.
Empty scales awnless.
Flowering scales i-nerved.
Panicle dense and spike-like, the spikelets markedly compressed laterally, ciliate
on the keel.
Panicle open or narrow, the spikelets not markedly laterally compressed, the keel glabrous.
Grain loosely enclosed in the pericarp, from which it readily separates and falls at maturity; flowering scales with no hairs at the base.
Empty scales minute; low arctic grass.
Empty scales evident.
Grain adherent to the pericarp and not separating from it at maturity; flower-
ing scale with a ring of long hairs at the base.
Flowering scales 3-5-nerved.
Stamen 1; flowering scale stipitate; palet usually i-nerved.
Stamens 3; flowering scale sessile; palet 2-nerved.
Rachilla not prolonged beyond the flowering scale.
• Empty scales shorter than flowering scale; spikelets large
Empty scales longer than the flowering scale; spikelets small.
Rachilla prolonged beyond the flowering scale.
Prolongation of the rachilla glabrous; flowering scale glabrous at the base,
and with a long awn just below the bifid apex.
Prolongation of the rachilla with long hairs; flowering scale awned at or below the middle.
Flowering scale membranous; spikelets 4" long or less.
Flowering scale chartaceous; spikelets 5"-6" long
Tribe VIII. Aveneae.
Spikelets deciduous; lower flower perfect, upper staminate, awned.
Spikelets not deciduous; empty scales persistent, flowering ones deciduous.
Spikelets of 2 perfect flowers; rachilla not prolonged beyond the upper one.
Spikelets 2-many-flowered; rachilla prolonged beyond the upper scale.
Awn of flowering scale dorsal, inserted below the teeth.
Flowers all perfect, or the upper ones staminate or wanting.
Spikelets less than 6" long; grain free, unfurrowed.
Flowering scales convex; awn arising from or below the middle.
Flowering scales keeled: awn arising from above the middle.
Spikelets over 6" long; grain furrowed, usually adherent to the scales.
Upper flower perfect, lower staminate, its scale strongly awned.
Awn from between the lobes or teeth of flowering scale, generally twisted.
Tribe IX. Chlorideae.
Spikelets with perfect flowers, or sometimes some of them rudimentary or unisexual.
Spikelets deciduous entire.
Spikelets narrow, lanceolate; rachis produced beyond the upper spikelet.
Spikelets broad, orbicular; rachis of the spike not produced.
Spikelets not deciduous entire; empty scales persistent; flowering scales deciduous.
One perfect flower in each spikelet (rarely 2 in no. 56).
No empty scales above the flower.
Spikes 2-6, digitate.
Spikes many, scattered.
One to several empty scales above the flower.
Lower empty scales 4; spike solitary, dense.
Lower empty scales 2.
Spikes in false whorls or closely approximate; scales long-awned.
Spikes remote, or the lowest only approximate.
Spikelets scattered or remote in long filiform spikes.
Spikelets crowded in short stout spikes.
Spikes 4 or less; spikelets numerous, 25 or more.
Spikes numerous, 12 or more; spikelets few, 12 or less.
2-several perfect flowers in each spikelet.
Spikelets densely crowded; spikes digitate.
Spikes with terminal spikelets.
Spikes with rachis extending beyond them in a naked point.
Spikelets distinctly alternating; spikes remote.
Branches of the inflorescence slender; spikelets less than 2" long, numerous, the
palets not gibbous.
Branches of the inflorescence stout, rigid; spikelets 4" long or more, few, the palets
gibbous at the base.
Spikelets with unisexual flowers, very unlike; plants dioecious.
Tribe X. Festuceae.
Rachilla with hairs longer than flowering scales enveloping them.
Rachilla and flowering scales glabrous, or if hairy the hairs shorter than the scales.
Stigmas barbellate; spikelets in clusters of 3-6 in axils of spinescent leaves.
Stigmas plumose; spikelets not in the axils of leaves; inflorescence various.
Spikelets of 2 forms, the fertile 1-3-flowered, surrounded by the sterile consisting of many
empty pectinate scales.
Spikelets all alike.
Flowering scales 1-3-nerved, rarely with faint additional intermediate nerves.
Flowering scales not coriaceous in fruit; seed beakless and not exserted.
Lateral nerves of the flowering scales pilose.
Internodes of rachilla long, the deeply 2-lobed flowering scale attached by a
long pointed callus, which is pilose on the outer surface,
Internodes of rachilla and callus of flowering scales short, the latter blunt.
Spikelets on pedicels of varying length, arranged in a contracted or open, simple or compound panicle.
Inflorescence a contracted or open panicle; leaf-blades not cartilaginous
Inflorescence a short congested raceme; leaf-blades with thick con-
spicuous cartilaginous margins.
Spikelets on short pedicels of approximately the same length, appressed to
the long branches of the simple panicle.
Lateral nerves of the flowering scales glabrous.
Callus of flowering scale conspicuously pubescent with long hairs.
Panicle contracted; flowering scales broadly oval, rounded at the apex.
Panicle open, diffuse; flowering scales lanceolate, acute.
Callus of the flowering scale glabrous.
Second empty scale very dissimilar from the first, broad and rounded at
Second empty scale similar to the first.
Panicle narrow, branches appressed.
Panicle dull, interrupted; rachilla articulated.
Panicle shining, dense, spike-like; rachilla continuous.
Panicle open, the branches more or less spreading.
Rachilla continuous; flowering scales deciduous in fruit.
Rachilla articulated; flowering scales and palets both deciduous with
the rachilla internodes.
Flowering scales coriaceous in fruit; seed beaked and exserted.
Flowering scales 5-many-nerved.
Flowering scales 3-toothed at the apex.
Flowering scales not 3-toothed at the apex.
Spikelets with 2 or more of the upper scales empty, broad and enfolding each
other, forming a club-shaped mass.
Spikelets with the upper scales flower-bearing, or if empty similar in shape to the other scales.
Keels of the palet winged or with a linear appendage.
Keels of the palet not winged or appendaged.
Stigmas placed at or near the apex of the ovary; flowering scales usually awnless, or awned in nos. 90 and 98.
Scales more or less strongly compressed and keeled.
Empty basal scales 3-6; spikelets flat, 2-edged
Empty basal scales 2; spikelets somewhat flattened.
Spikelets unisexual; plant dioecious.
Spikelets arranged in 1-sided dense capitate clusters at the end
of the branches; flowering scales awned
Spikelets not arranged as above; flowering scales awnless.
Rachilla of the spikelets glabrous, or with webby hairs; flowering scales scarious-margined.
Spikelets cordate at the base, large.
Spikelets not cordate, usually small.
Empty scales projecting beyond the uppermost
flowering ones; arctic grass
Empty scales shorter than the uppermost flowering
Rachilla of the spikelets hirsute, extending into a hairy appendage; flowering scales membranous.
Scales rounded on the back, at least below.
Flowering scales with basal ring of hairs, apex toothed.
Flowering scales naked at the base.
Flowering scales obtuse or subacute and scarious at the apex, usually toothed.
Manifestly 5-7-nerved; styles present.
Obscurely 5-nerved; no styles.
Flowering scales acute, pointed, or apex awned.
Stigmas arising below apex of the ovary; scales rarely awnless.
Tribe XI. Hordeae.
Stigma 1; spike unilateral; spikelets 1-flowered, narrow.
Stigmas 2; spikes symmetrical.
Spikelets solitary at the notches of the rachis.
Flowering scales with their backs turned to the rachis.
Flowering scales with their sides turned to the rachis.
Spikelets 1- or 2-flowered, in slender articulate spikes.
Spikelets 2-many-flowered, in stout inarticulate spikes.
Spikelets 2-6 at each joint of the rachis; scales mostly long-awned.
Spikelets 1-flowered, or with the rudiment of a second flower.
Rachis of the spike articulated, readily breaking up.
Rachis of the spike continuous, not breaking up.
Empty scales a little smaller than the flowering ones.
Empty scales very small or none.
Tribe XII. Bambuseae.
Tall canes with large flat spikelets in panicles or racemes.