rete) MISC. PUBLICATION 243, U.S. DEPT. OF AGRICULTURE 
First glume about as long as the second or a little shorter. 
Beak of lemma 3 to 4 mm long, distinctly twisted_-8. A. NEGLECTA. 
Beak of lemma, if present, not twisted. 
Awns a maturity about equally divergent, not spirally contorted 
at base. 
Blades flat at least toward the base. 
Culms mostly more than 1 m tall; blades 3 to 5 mm wide. 
9. A. ERECTA. 
Culms mostly less than 70 cm tall; blades mostly not more than 
LEN WA Ge inners ee ey er ee 10. A. VILFIFOLIA. 
Blades involute. 
Blades short and stiff, mostly less than 3 cm long, usually 
approximate in pairs; culms very stiff and wiry. 
11. A. CURTIFOLIA. 
Blades mostly more than 5 cm long, not approximate in pairs. 
Panicle loose; awns 2 to 3 cm long__12. A. PORTORICENSIS. 
Panicle rather dense; awns 1 to 2.5 cm long. 
Callus of lemma nearly 2 mm long; first glume 1 cm long; 
lemma a little longer than the glumes; awns 2 cm long. 
A. CHASEAE. 
Callus of lemma about 0.5 mm long. 
Culms erect; blades as much as 30 em long; first glume 
about 7 mm long; lemma about 8 mm long; awns 
1.5 tow. dS emulong. 2 sae 14. A. SWARTZIANA. 
Culms spreading and branching at base; blades 5 to 
15 cm long; first glume 4 to 5 mm long; lemma 
6 to 7 mm long; awns 1 to 1.5 cm long. 
15. A. COGNATA. 
Awns at maturity unequally divergent or spirally contorted at 
base. 
Central awn horizontally spreading or somewhat reflexed, the 
lateral awns erect; awns not contorted at base; blades flat 
toward: baseers.- 20. ja ee ee SO oh ee 16. A. AFFINIS. 
Central awn not more divergent than the others; awns all con- 
torted at base; blades involute. 
Awns 1.5 to 3 cm long. 
Lemma 7 mm long, glabrous, the awns strongly contorted 
at base; plants rather stout, the blades as much as 
20 cm long, the panicles as much as 30 cm long. 
17. A. BRITTONORUM. 
Lemma 10 mm long, scabrous on the upper half, the awns 
weakly contorted at base; plants slender, the blades 
5 to 10 cm long, the panicles 7 to 15 em long. » 
18. A. CALCICOLA. 
Awns about 1 em long. 
First glume glabrous on the keel_________-_ 19. A. ROSEI. 
First glume scabrous on the keel__-_--- 20. A. REFRACTA, 
1. Aristida ternipes Cav., Icon. Pl. 5:46. 1799. Panama. 
SPIDER GRASS. 
Streptachne scabra H. B. K., Nov. Gen. et Sp. 1: 124. pl. 40. 
1815. Mexico. 
Aristida scabra Kunth, Rév. Gram. 1: 62. 1829. 
2 Se cubensis A. Rich., in Sagra, Hist. Cuba 11: 311. 1850. 
uba. 
Erect perennial; culms 50 to 100 cm tall; blades flat, involute above, 
tapering into a fine point, 2 to 3 mm wide; panicle open, one-third 
to half the entire length of the culm, the branches few, distant, 
spreading, scabrous, mostly naked at base; spikelets appressed at the 
ends of the branches; glumes about equal, 8 to 10 mm long; lemma 
eradually narrowed into a laterally compressed scabrous falcate beak, 
this extending into a single arcuate awn 10 to 15 mm long; lateral 
awns minute or obsolete. In arid situations the blades may be narrow 
and nearly all involute (fig. 52). 
