HITCHCOCK AND CHASE — GRASSES OF THE WEST INDIES. 325 



Spikelets hispid and with 2 crateriform glands on the sterile 



lemma 39. P. pulchellum. 



Spikelets glabrous, glandless ; second glume and sterile lemma 

 boat-shaped. 

 Blades not over 5 cm., usually 2 or 3 cm., long; second glume 

 rather blunt and shorter than the sterile lemma. 



37. P. stolonif erum. 

 Blades 5 to 11 cm. long; second glume acute, nearly equaling 



the sterile lemma 38. P. frondescens. 



Blades linear, often elongate ; spikelets glabrous. (Laxa in part.) 

 Spikelets not expanded at maturity by an enlarged sterile 

 palea, pointed; nodes densely pubescent. 



30. P. polygonatum. 

 Spikelets more or less expanded at maturity by the enlarged 

 sterile palea, mostly blunt. 



Blades narrowed toward the base 34. P. laxum. 



Blades cordate or truncate at the base. 



Spikelets 2 mm. long; panicle branches erect or nearly so. 



35. P. stevensianum. 

 Spikelets not over 1.6 mm. long, usually less; panicle 

 branches spreading or ascending. 

 Panicles one-third to half as wide as long ; spikelets not 

 conspicuously secund, somewhat irregularly dis- 

 posed ; blades cordate-clasping 33. P. boliviense. 



Panicles rarely one-fourth as wide as long; spikelets 

 conspicuously secund and regularly disposed. 

 Culms as much as 2 meters long ; panicles 25 to 30 cm. 



long; Trinidad 31. P. millefiorum. 



Culms not over 1 meter long ; panicles 5 to 15 cm. long. 



32. P. pilosum. 



Spikelets in open or sometimes (Ageostoidia, Tenera) in contracted 



or congested panicles, but not in 1-sided spikelike racemes. 



Sterile palea enlarged and indurate at maturity, expanding the 



minute spikelets; spikelets clustered along the ends of the 



branches 36. P. exiguiflorum. 



Sterile palea if present not enlarged. 

 Fruit sparsely silky-pubescent ; first glume very small, not over 

 one-fourth the length of the small obovate blunt glabrous 



spikelets 40. P. schiffneri. 



Fruit glabrous ; first glume usually more than one-third the length 



of the spikelet, if shorter the spikelets not obovate nor blunt. 



First glume short, blunt; spikelets pointed; base of culm 



usually decumbent, rooting at the nodes. (Dichotomi- 



flora in part.) 



Fruit not acuminate; panicles rarely over 18 cm. long. 



12. P. aquaticum. 

 Fruit acuminate; panicles often 40 cm. long; culms succu- 

 lent; aquatic 13. P. elephantipes. 



First glume usually more than one-third the length of the 

 spikelet. 

 Plants forming conspicuous ha»d creeping scaly rhizomes. 

 (Virgata.) 



