HITCHCOCK AND CHASE-^-GEASSES OF THE WEST INDIES. 305 



Rachis 2 to 2.5 mm. wide; culms mostly decumbent at 

 base ; spikelets abruptly minutely pointed. 

 Spikelets glabrous, about 2.5 mm. long. 



9. P. denticulatum. 

 Spikelets pubescent, 3 to 3.2 mm. long. 



8. P. pubiflorum. 

 Rachis less than 1 mm. wide. 



Blades firm, more or less involute-margined, narrower 

 at the base than the summit of the sheath. 

 Culms 0.5 to 1 meter tall, not geniculate; blades 

 elongate; spikelets pubescent (rarely glabrous). 



35. P. glabrum. 



Culms 20 to 40 cm. long, spreading, geniculate below ; 



blades not over 10 cm. long ; spikelets glabrous. 



36. P. bakeri. 



Blades thin, flat, mostly more or less ciliate, broader 



at the base than the summit of the sheath. 



Spikelets glabrous ; blades linear, scarcely 4 mm. 



wide, firm; culms stiffly erect from a short 



knotty rhizome 37. P. rigidifolium. 



Spikelets minutely pubescent (exceptionally glab- 

 rous) ; blades lanceolate. 

 Blades short-pubescent and pilose on the upper 



surface 40. P. debile. 



Blades glabrous on the surface or exceptionally 

 with a few hairs. 

 Spikelets ovate to suborbicular ; blades lax. 



39. P. ciliatif olium. 

 Spikelets obovate ; blades somewhat stiff. 



38. P. propinquum. 

 Spikelets not over 1.8 mm. long, usually less. 

 Plants annual, tufted, pilose; blades linear. 



Spikelets orbicular or nearly so, at least some of them 



sprinkled with globular hairs 45. P. multicaule. 



Spikelets elliptic, glabrous 46. P. parvifiorum. 



Plants perennial. 



Culms creeping or decumbent and rooting at the nodes. 



Spikelets pubescent 49. P. reptatum. 



Spikelets glabrous. 

 Blades appressed-pubescent, commonly 8 to 10 cm. 



long ; spikelets 1.8 mm. long 42. P. nutans. 



Blades glabrous ; spikelets 1.4 mm. or less long. 



Racemes solitary, 1 to 1.2 cm. long 31. P. breve. 



Racemes 2 or 3, 2 to 3 cm. long; spikelets minute, 



yellowish 48. P. orbiculatum. 



Culms tufted, not creeping nor decumbent. 

 Racemes 2 to 10. 

 Nodes appressed-pubescent; spikelets usually solitary. 



^uocvi&o, 29 - P - Poiretii. 



Nodes^glabrous r spikelets in pairs. 



Spikelets about 1.3 mm. long, obovate, blunt, 

 crowded, glandular-pubescent. 

 t 34. P. simpsoni. 



