HITCHCOCK AND CHASE GRASSES OF THE WEST INDIES. 323 



Spikelets pubescent. 

 Spikelets attenuate at base, mostly prominently pustulose ; blades nar- 

 row, stiff, strongly nerved, tapering from base to apex. (Angusti- 



FOLIA.) 



Nodes bearded ; plants grayish-villous ; autumnal blades flat, rather 



soft 54. P. chrysopsidifolium. 



Nodes not bearded ; plants villous only at base, or nearly glabrous ; 

 autumnal blades involute. 



Spikelets 3 to 3.5 mm. long, pointed 55. P. fusiforme. 



Spikelets less than 3 mm. long, not pointed or obscurely so. 



Plants glabrous or nearly so ; autumnal culms erect ; spikelets 

 subsecund along the subereet panicle branches. 



57. P. neuranthum. 

 Plants pubescent, at least on the lower half. 



Spikelets not over 2 mm. long ; vernal blades 4 to 6 cm. long ; 



autumnal blades much crowded, falcate 53. P. aciculare. 



Spikelets 2.2 to 2.4 mm. long; vernal blades 7 to 12 cm. long; 



autumnal blades not falcate 56. P. arenicoloides. 



Spikelets not attenuate at base, not pustulose ; blades lanceolate to 

 linear-lanceolate but usually less than 10 times as long as broad. 

 Sheaths glabrous. 



Spikelets subglobose or pyriform. 



Blades erect, 7 to 13 cm. long, 7 to 14 mm. wide ; spikelets 



spheroid 65. P. erectifolium. 



Blades spreading, rarely over 5 cm. long and 5 mm. wide; 

 spikelets pyriform; autumnal form bushy-branching. (Lan- 



CEARIA.) 



Spikelets 1.5 to 1.6 mm. long 68. P. portoricense. 



Spikelets 2 mm. long 69. P. lancearium. 



Spikelets elliptic to obovate. 

 Nodes glabrous. 



Spikelets 2.8 to 3 mm. long; blades commonly 1 cm. wide, not 



white-margined 72. P. joorii. 



Spikelets not over 1.5 mm. long; blades not over 6 mm. wide, 

 with a cartilaginous white margin. 



66. P. albomarginatum. 



Nodes bearded ; blades not white-margined ; spikelets 2 mm. long. 



Sheaths, at least the upper, viscid-spotted ; autumnal phase 



erect or reclining 58. P. nitidum. 



Sheaths not viscid-spotted ; autumnal phase decumbent, with 







flabellate-fascicled branches 59. P. m.ultirameuni. 



Sheaths pubescent. 



Culms usually 75 cm. or more tall; foliage velvety-pubescent. 

 Vernal culms erect or ascending ; plants velvety throughout ; 



spikelets about 2.5 mm. long 70. P. scoparium. 



Vernal culms decumbent at base; upper sheaths more or less 



glabrate; spikelets less than 2 mm. long 71. P. viscidellum. 



Culms not over 50 cm. tall. 



Plants conspicuously villous throughout 64. P. acuminatum. 



Plants appressed-pubescent on the culms and sheaths ; blades 

 glabrous above. 



Spikelets 1.2 to 1.3 mm. long 62. P. leucothrix. 



Spikelets not over 1 mm. long 63. P. wrig'htianum. 



