726 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



peduncle, or single, in pairs, or sometimes in threes or fours, the com- 

 mon peduncle usually enclosed by a spathelike sheath, these sheaths 

 often numerous, the whole forming a compound inflorescence, 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 sterile pedicels. 



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

 good forage grasses but may soon become woody toward maturity 

 and thus decrease in value. Andropogon Jurcatus, bluejoint turkey- 

 foot, is the most important constituent 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. Prairie beard- 

 grass (A. scoparius) is also a common constituent of wild hay. 



Racemes solitary on each peduncle. Apex of rachis joints obliquely cup-shaped. 



Section 1. Schizachyrium. 

 Racemes 2 to numerous on each peduncle. 



Racemes 2 to several on each peduncle, digitate; joints of rachis slender, some- 

 times 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 flat, 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. rtrtiflorus. 



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. cirrattts. 



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). 

 Lower sheaths not broad nor conspicuously keeled; hairs on rachis and 



pedicels 2 to 3 mm long 6. A. scoparius. 



Lower sheaths relatively broad, crowded and strongly keeled. 

 Sheaths and blades glabrous; pedicellate spikelet reduced. 



7. A. LITTORALIS. 



Sheaths and blades villous; pedicellate spikelet prominent. 



10. A. DIVERGENS. 



Culms solitary or few together; creeping rhizomes developed. 

 Sessile spikelets 5 to 7 mm long; sterile spikelets much reduced. 



8. A. STOLONIFER. 



Sessile spikelets 8 to 10 mm long; sterile spikelets mostly not much 

 reduced 9. A. maritimus. 



Section 2. Arthrolophis 



la. Pedicellate spikelet staminate, similar to the sessile spikelet. 



Rhizomes short or wanting; rachis joint and sterile pedicel ciliate, the joints 

 short- hispid at base; awn of sessile spikelet 1 to 2 cm long. 



11. A. FURCATUS. 

 Rhizomes well developed; rachis joint and sterile pedicel densely long- villous; 

 awn of sessile spikelet rarely more than 5 mm long, often obsolete. 



12. A. HALLII. 

 lb. Pedicellate spikelet reduced to 1 or 2 glumes, or obsolete, the pedicel only 

 developed; racemes silky- villous. 



