HITCHCOCK AND CHASE — GRASSES OF THE WEST INDIES. 303 



Spikelets not lacerate-margined. 

 Inflorescence a large flabellate panicle of numerous racemes, the spikelets 

 solitary. 



Spikelets glabrous 51. P. fasciculatum. 



Spikelets with long silky hairs on the margin ; racemes very slender. 



60. P. saccharoides. 

 Inflorescence not flabellate, or if slightly so the spikelets in pairs. 

 Racemes 2, conjugate at the summit of the culm, rarely a third below. 

 Spikelets elliptic or narrowly ovate. 



Culms erect, not stoloniferous nor rhizomatous 20. P. neesiiv 



Culms ascending or erect from creeping stolons or rhizomes. 

 Second glume pubescent ; spikelets somewhat turgid. 



7. P. distichum. 

 Second glume and sterile lemma glabrous; spikelets flattened. 

 Blades erect or ascending, involute-setaceous__6. P. distachyon. 

 Blades spreading, tapering from base to apex, the margins in- 

 volute , 5. P. vaginatuin. 



Spikelets suborbicular, broadly ovate or obovate. 



Spikelets concavo-convex, sparsely long-silky around the margin; 



plants stoloniferous 50. P. conjugatum. 



Spikelets plano-convex, not silky-margined. 



Spikelets 1.5 mm. or less long, more or less pubescent. 

 Plants annual ; spikelets or some of them sprinkled with globular 



hairs 45. P. multicaule. 



Plants perennial ; spikelets minutely pubescent. 



47. P. clavuliferum. 

 Spikelets 1.8 to 3 mm. long, glabrous. 



Spikelets golden brown, transversely marked with dark lines. 



13. P. serpentinum. 

 Spikelets green, not marked. 



Sheaths pubescent ; spikelets about 1.8 mm. long. 



12. P. pumilum. 

 Sheaths glabrous or sparsely ciliate only. 



Spikelets less than 2.5 mm. long 11. P. minus. 



4 Spikelets 2.5 to 3 mm. long 10. P. notatum. 



Racemes 1 to many, racemose or fascicled on the axis, not conjugate. 

 Second glume wanting ; sterile lemma dark crimson. 



59. P. pulchellum. 

 Second glume present. 

 First glume present on at least one of the pair of spikelets. 



Spikelets pubescent 43. P. ciliif erum. 



Spikelets glabrous. 



Spikelets 1.5 mm. long 41. P. decumbens. 



Spikelets 2.6 to 3 mm. long. 



Plants with hard scaly rhizomes 57. P. unispicatum. 



Plants more or less stoloniferous but having no rhizomes. 



58. P. pilosum. 

 First glume normally wanting (rarely present on occasional spike- 

 lets). 

 Fruit dark brown and polished (see also no. 52 with brown but not 

 polished fruit). 

 Plants annual. 

 47877°— 17 4 



