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



29. Andropogon perforatus Trin. (Fig. 1660.) Culms densely 

 tufted, geniculate at base, 50 to 100 cm tall, simple or -with a few- 

 leafy shoots at base; nodes from obscurely appressed-pubescent to 

 densely short-bearded; blades 2 to 4 mm wide, the apex attenuate; 

 racemes few to several, mostly 5 to 7 cm long, one or more of them on 

 slender individual peduncles aggregate on a short axis, the common 

 peduncle usually long-exserted ; margins of rachis joints and pedicels 

 densely long- villous ; sessile spikelet 4 to 6 mm long, short-pilose at base, 

 the first glume sparsely hairy and with a small pit like a pinhole ; awn 

 twisted below, geniculate, 2 to 2.5 cm long; pedicellate spikelet reduced. 

 01 — Mesas, rocky hills, and dry woods, southern Texas; Mexico. 



30. Andropogon barbinodis Lag. (Fig. 1661.) Culms tufted, 

 40 to 120 cm tall, spreading to ascending, often branching below, the 

 nodes bearded with short spreading hairs; sheaths sparsely hairy in 



the throat, foliage otherwise glabrous or 

 nearly so, the blades 2 to 7 mm wide, sca- 

 brous; panicles from rather long-exserted 

 to included at base, those of the branches 

 often partly included in dilated sheaths, 

 silvery to creamy white, silky, subflabellate, 

 mostly 7 to 10 cm long; racemes several to 

 many, or sometimes few on the branches, 

 2 to 6 cm long, the common axis usually 

 shorter than the racemes, rarely longer; 

 rachis joints and pedicels copiously long- 

 villous, the hairs on the average longer than 

 in A. saccharoides ; spikelets 5 to 6 mm long, 

 the awn twisted below, geniculate, 20 to 

 25 mm long; pedicellate spikelet reduced. 

 21 — Mesas, rocky slopes, and open 

 ground, Oklahoma and Texas to California 

 and Arizona, south through Mexico (fig. 

 1662). Has been confused with A. saccha- 

 roides, differing chiefly in the subflabellate 

 panicle and larger spikelets. 



31. Andropogon saccharoides Swartz. 

 Silver beardgrass. (Fig. 1663.) Culms tufted, 60 to 130 cm tall, 

 erect or ascending, often brandling below, the nodes from appressed 

 hispid to glabrous; foliage commonly glaucous, glabrous or nearly 

 so, the blades 3 to 6 mm wide; panicle long-exserted or those of the 

 branches short-exserted, silvery white, silky, dense, oblong, mostly 7 

 to 15 cm long; racemes 2 to 4 cm long, the common axis mostly at 

 least twice as long, but readily breaking ; rachis joints and pedicels long- 

 villous; spikelets about 4 mm long, the delicate awn twisted below, 

 geniculate, 10 to 15 mm long; pedicellate spikelet reduced. % — 

 Prairies and rocky slopes, especially in limestone areas, Missouri to 

 Colorado, and Alabama to Arizona and southern California (Topango 

 Canyon); Mexico and West Indies to Brazil (fig. 1664). Our plants, 

 which have been differentiated as A. torreyanus Steud., are more 

 freely branching than the typical form of the West Indies. 



32. Andropogon exaristatus (Nash) Hitchc. (Fig. 1665.) Re- 

 sembling A. saccharoides; panicle slender, spikelets slightly smaller, 

 awnless or nearly so; rare. % — Low open ground, southern 

 Louisiana and eastern Texas, 



Figure 1660.— Andropogon perforatus, 

 X 1. (Hitchcock 5218, Tex.) 



