GRIFFITHS THE GRAMA GRASSES. 353 



Spikelets not pectinately arranged. (Subgenus 

 Atheropogon.) 



Spikes of 1 spikelet 35. B. uniflora* 



Spikes of more than 1 spikelet. 

 Plants annual. 



Leaves and sheaths tuberculate-hairy 18. B. alavrosana. 



Leaves and sheaths not tuberculate- 

 hairy 19. B. aristidoides. 



Plants perennial. 



Sheaths densely hairy 20. B. pringlei. 



Sheaths not densely hairy. 

 Glumes densely hairy. 



Sterile lemma trifid, long-awned. 21. B. chondrosioides. 

 Sterile florets two or three, with 

 well developed lemmas 



(variable) 22. B. eludens. 



Glumes not densely hairy. (See 

 continuation.) 

 (Continuation.) 

 Sterile florets distinctly 2 or more. 



Plants stoloniferous 23. B. megapotamica. 



Plants cespitose. 



Plants low, hairy 24. B. texana. 



Plants tall, smooth 25. B. lophostachya. 



Sterile floret 1 or with additional rudimentary one. 

 Second floret trifid and naked, not glumaceous. 

 Lateral awns short. 



Proximal spikelets not rudimentary 26. B. acuminata. 



Proximal spikelets rudimentary 27. B. vaneedeni. 



Lateral awns nearly as long as central one 28. B. americana. 



Second floret glumaceous. 



Second floret mostly perfect, the first sterile. 



Plants smooth 29. B. repens. 



Plants more or less prominently papillose-hairy. 

 Spikes and spikelets alike (Continental Amer- 

 ica). 

 Plants stout with harsh rhizomato us base . 30. B. radicosa. 

 Plants more delicate, cespitose or genicu- 

 late. . ._. 31. B. filiformis. 



Spikes and spikelets very variable (West 



Indies) 32. B. heterostega. 



Second floret sterile, the first fertile. 



Spikes about 12. .-: 33. B. disticha. 



Spikes more numerous. 



Spikelet with rudiment of a third 



floret 34. B. pilosa. 



Spikelet with no rudiment of a 



third floret 36. B. curtipendula. 



a Immature forms of several species belonging here are likely to be looked for 

 under Chondrosium., 



