495 
ate, acute, usually broader than the first and nearly equaling it in 
length, 3-nerved, membranaceous or coriaceous, except the slender green 
keel; the third glume empty, hyaline; the fourth (floral glume) hyaline 
below, entire or bifid, awned; palet small or wanting.—A large genus 
comprising many subgenera or sections, three of which are represented 
in Texas, 
\ 1. Racemes slender, solitary, terminal on long peduncles; the thickened clavate pedicels 
and joints of the rachis with a cup or a tooth-like appendage at the apex: floral glume 
cleft to the middle or beiow, awned from the sinus. —SCHIZACHY RIUM. 
* Racemes close flowered with appressed spikelets. 
1. A. hirtiflorus Kth., var. FEENSIS(Fourn.) Hack. Culms 5 to 10 dm. high, slen- 
der, smooth, branched above: racemes 3 to 5,5 to 8 em, long, of 8 to 12 joints; rachis 
villous with hairs about 2 mm. long; margin of cup toothed and ciliate: sessile 
spikelet 8 to 10 mm, long; first glume lance-linear, 2-toothed, seabrid, sparsely hairy, 
5 to T-nerved; awn 1 to 1.5 cm. long.—Western Texas to Arizona and Mexico, 
2. A. cirratus Hack, Culms 4 to 8 dm. high, erect, slender, smooth, branched 
above: racemes 3 to 5,5 to 7 em. long, of 8 to 12 joints; rachis smooth except the 
ciliate margin of the cup, and sometimes a slight tuft of hairs at the base of the joint; 
pedicel of neutral flower bearded near the apex: sessile spikelet 7 mm. long; first 
glume 2-toothed, chartaceous below the middle, 9-nerved, nearly smooth; awn 1 em. 
long.—Western Texas to Arizona and Mexico, 
8 A.tener Kth. Culms 4 to 8 dm, high, very slender, with long filiform branches 
from near the base: leaves soon involute filiform, smooth: racemes 3 to 8, slender, 4 
to 8 em. long, of 10 to 15 joints, often nodding on the long peduncles; joints of the 
rachis bearded at the base and on the rim of the cup, otherwise smooth; pedicels 
bearded near the apex: sessile spikelet 5 mm. long; first glume subacute, 5-nerved, 
smooth; awn bent, 1.5 cm. long.—Near the mouth of the Rio Grande. 
** Racemes very hairy, loosely flowered with divergent spikelets. 
4, A. scoparius Michx. Culms 5 to 10 dm. high, smooth and wiry, loosely branch- 
ing above; branches single or in fascicles, sometimes subdivided: racemes usually 
numerous, 3 to 4 em. long, of 4 to 6 joints slender below, curved or zigzag at maturity, 
loosely bearded above; pedicels slender, bearded above, bearing a rudimentary 
spikelet: sessile spikelet about 7 mm. long; first glume slightly bifid, nearly smooth, 
5 to T-nerved; awn 1 em. long.--Common in the river valleys throughout the 
United States east of the Rocky Mountains, Var. MARITIMUS Hack, is like the spe- 
cies, but more robust and often pubescent throughout; differing especially in the 
larger spikelets (9 to 10 mm. long) and the more abundant silky hairs on the rachis 
and pedicels.—Eastern Texas to Florida. ~ 
§ 2. Racemes in pairs, rarely digitate or panicled, the lateral ones sessile: rachis joints 
and pedicels not translucent, a leaf-like bract below the first joint: floral glume bifid 
or 2-toothed. —ARTHROLOPHIS. 
* Racemes very hairy, loosely flowered, with divergent spikelets; rachis joints and pedicels 
not clavate: floral glume slightly bidentate. 
+ Sheathing bract at the base of the racemes equaling or longer than the racemes. 
5. A. glomeratus (Walt.) B.S. P. Culms 5 to 15 dm. high, somewhat compressed 
below, smooth, much branched, especially near the summit; branches usually fasei- 
culate; panicle dense, silky, 1 to5dm. long, of somewhat interrupted cymose clusters ; 
racemes in pairs, 2 to 3 cm, long, of 5 to 8 joints, usually exceeded by the lanceolate 
