MANUAL OF THE GRASSES OF THE UNITED STATES 749 



154. ANDROPOGON L. Beardgrass 



Spikelets in pairs at each node of an articulate rachis, one sessile and per- 

 fect, the other pedicellate and either staminate, neuter, or reduced to the 

 pedicel, the rachis and pedicels of the sterile spikelets often villous, sometimes 

 conspicuously so; glumes of fertile spikelet coriaceous, narrow, the first 

 rounded, flat, or concave on the back, the median nerve weak or wanting, the 

 second laterally compressed; sterile lemma shorter than the glumes, empty, 

 hyaline; fertile lemma hyaline, narrow, entire or bifid, usually bearing a bent 

 and twisted awn from the apex or from between the lobes; palea hyaline, small 

 or wanting; pedicellate spikelet awnless, sometimes staminate and about as 

 large as the sessile spikelet, sometimes consisting of 1 or 2 reduced glumes, 

 sometimes wanting, only the pedicel present. Rather coarse grasses (perennial 

 in the United States), with solid culms, the spikelets arranged in racemes, these 

 numerous, aggregate on an exserted peduncle, or single, in pairs, or sometimes 

 in threes or fours, the common peduncle usually enclosed by a spathelike 

 sheath, these sheaths often numerous, the whole forming a compound in- 

 florescence, usually narrow, but sometimes in dense subcorymbose masses. 

 Standard species, Andropogon distachyus L. Name from Greek aner (andr-), 

 man, and pogon, beard, alluding to the villous pedicels of the staminate or 

 sterile spikelets. 



Several of the species, especially in the Southwest, are regarded as good 

 forage grasses but may soon become woody toward maturity and thus de- 

 crease in value. Andropogon gerardi, big bluestem, is the most important con- 

 stituent of the wild hay of the prairie States. The amount is decreasing 

 rapidly because the rich land upon which it grows is being converted into 

 cultivated fields. Little bluestem (A. scoparius) is also a common constituent 

 of wild hay. 



Racemes solitary on each peduncle; rachis joints oblique and hollow at the summit. 



Section 1. Schizachyrium. 

 Racemes 2 to numerous on each peduncle. 



Racemes 2 to several on each peduncle, digitate; joints of rachis slender, sometimes with 



a shallow groove on one side Section 2. Arthrolophis. 



Racemes several to numerous (rarely few) in a leafless panicle usually on a relatively long 

 axis, the joints of the rachis fiat, the margins thick and ciliate, the center very thin. 



Section 3. Amphilophis. 



Section 1. Schizachyrium 



Blades slender, terete, the upper surface a mere groove 1. A. gracilis. 



Blades flat or folded, not terete. 



First glume of sessile spikelet pubescent 3. A. hirtiflorus. 



First glume of sessile spikelet glabrous. 



Internodes of rachis relatively thick, glabrous or ciliate at base and near apex only; 

 racemes straight. 



Sessile spikelet 4 mm. long; blades about 1 mm. wide 2. A. tener. 



Sessile spikelet 6 to 9 mm. long.; blades mostly 2 to 3 mm. wide. 



Sterile pedicel ciliate from below the middle to the apex; sterile spikelet about 3 



mm. long, the awn somewhat exserted 4. A. semiberbis. 



Sterile pedicel ciliate only at the apex; sterile spikelet about 5 mm. long, the awn 



wanting or included 5. . A. cirratus. 



Internodes of rachis and sterile pedicels slender, villous throughout or nearly so; 



racemes flexuous. 



Culms tufted; rhizomes wanting (base sometimes slightly rhizomatous in A. littoralis). 



Sheaths and blades glabrous or nearly so (occasionally sparsely to conspicuously 



pilose in A. scoparius); pedicellate spikelet usually much reduced. 



Racemes nearly straight, densely villous, the hairs obscuring the rachis and 



spikelets; blades 5 to 9 cm. long, spreading 6. A. niveus. 



