5 
(1) Awn usually trifid, the branches divaricate...........-... we eeeeeeee ARISTIDA, 44 
(2) Awn simple, twisted ; callus mostly acute............--.-------------- Sripa, 49 
(3) Awn simple, straight, deciduous; callus short, obtuse. ............ ORYZOPSIS, 55 
(4) Awn wanting; flowering glume without a callus ..-..-.20-- 2.2.0.2. MILIUM, 56 
(2) Subtribe HUAGROSTE. 
Glumes membranaceous, the lower rarely strongly conduplicate, the 
floral one with or without a dorsal awn; sometimes with a minute or con- 
spicuous rudiment. 
(1) Spikelets strongly conduplicate; palet l-nerved; stamen 1; sometimes with a 
rudiment.... ..---. 2-2-2222 eee eee eee eee eee eee peewee cee CINNA, 57 
(2) Flowering glume 1- (rarely 3-) nerved; grain loosely inclosed or naked; no rudi- 
MONE 2. 2.2. eee eee ee ee eee eee ee ee eee cece cee eee SPOROBOLUS, 59 
(3) Empty glumes long-awned ; no rudiment ....-... 2... -...-----. POLYPOGON, 57 
(4) Empty glumes chartaceous and hairy; flowering glume strongly awned under 
the apex ; rudiment present...--. 2. 2c ee eee ee ee ee THURBERIA, 58 
(5) Flowers large, spicate or closéiy panicled ; not awned ..--...--. EPICAMPES, 58 
(6) Flowers large, panicle contracted; Arctic grasses........---. ARCTAGROSTIS, 59 
(7) Floral glume mucronate or awned from the apex; no rudiment. 
MUHLENBERGIA, 64 
(8) Empty glumes minute; floral glume large and with a short awn; rachilla much 
prolonged and terminated by a minute rudiment ........ BRACHYELYTRUM, 71 
(9) Empty glumes longer than the floral glume; rarely with a minute rudi- 
MeNt. .-.. eee eee ee ee ce ee eee eee cee eee teens AGROSTIS, 72 
(10) Floral glume with a delicate awn. below the apex, many times longer than the 
glume .. 0... 22. eee ee ee ee ee eee ee cee cee ne eee APERA, 78 
(11) Empty glumes saccate at the base, many times longer than the floral 
glume «2.2.2. 0.2.2. eee eee eee ce ne eee ee cee ces GASTRIDIUM, 78 
(12) Flowers generally with many fine hairs from the callus at the base and with 
a hairy rudiment; the floral glume and palet (except in section Calamovilfa) 
thin and membranaceous. .. 2.2. 22-2. ee eee ee cee ee eee CALAMAGROSTIS, 73 
(13) Floral glume and palet chartaceous; floral glume awnless; panicle spike- 
like. .........20..--6-.- we ee eee eee ee eee eens AMMOPHILA, 85 
(3) Subtribe PHLEOIDE 4. 
Flowering glume usually hyaline or membranaceous at maturity, at 
least more delicate than the empty glumes; grain loosely or not at all 
inclosed. 
A. Spikelets in a spikelike panicle, 
I, Awns none; spikes short and scarcely exserted ...-.....--.- HELEOCHLOA, 85 
II. Glumes somewhat truncate, mucronate, or short-awned, spike cylindric. 
PHLEUM, 86 
III. Empty glumes united at the base, the floral one awned on the back; palet 
none; spike cylindric ....... 2.2 eee eee ee ee eee eee wees ALOPECURUS, 386 
IV. Lower glumes with 2awnlike teeth, the upper with 1 -.......... Lycurus, 88 
B. Spikelets minute; empty glumes wanting, the floral usually deciduous. 
COLEANTHUS, 88 
C. Spikelets in a narrow panicle ; empty glume short......--...----- Puiprpsia, 89 
TRIPSACUM Linn. 
Flowers monecious in jointed spikes, the upper part male and the 
lower female. The upper or male spikelets sessile, in pairs at each joint 
of the triangular rachis; each spikelet with 2 membranaceous male 
