20 



CONTKIBUTIONS FKOM THE NATIONAL HEEBAEIUM. 



Racemes appressed; fruit nearly as long as the 

 spikelet. 



Spikelets silky-villous, pointed 194. 



Spikelets glabrous, obtuse 192. 



First glume much shorter than the sterile lemma. 

 Spikelets hispid and with two crateriform glands on 

 the sterile lemma. 

 Spikelets not over 2 mm. long; blades not over 



4 cm. long 66. 



Spikelets 3.6 mm. long; blades 4 to 10 cm. long. . 67. 

 Spikelets glabrous. 

 Blades lanceolate to ovate-lanceolate; glumes 

 strongly carinate; spikelets 2.3 to 2.8 mm. 

 long; tropical species. 

 Blades not over 5 cm., usually 2 to 3 cm. long; 

 second glume rather blunt and shorter than 



the sterile lemma 64. 



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



slightly shorter than the sterile lemma 65. 



Blades linear, often elongated ; glumes not carinate 

 or but slightly so. 

 Spikelets not over 1.5 mm. long. 



Spikelets pointed, not expanded at maturity 



by an enlarged sterile palea 58. 



Spikelets blunt, expanded at maturity by the 

 enlarged sterile palea. 

 Rachis bearing slender bristles (these want- 

 ing in exceptional specimens); nodes 



usually villous 59 . 



Rachis without bristles; nodes glabrous. ... 60. 

 Spikelets 2.5 mm. or more long. 



Axis pilose 57. 



Axis not pilose. 



Fruit transversely rugose See 



Fruit not rugose 193. 



Spikelets in open or sometimes in contracted or congested 

 panicles, but not in spike-like racemes. 

 Basal leaves usually distinctly different from those of 

 the culm, forming a winter rosette; culms at first 

 simple, the spikelets of the primary panicle not per- 

 fecting seed, later usually becoming much 

 branched, the small secondary panicles with cleis- 

 togamous, fruitful spikelets See. subgenus 



Basal leaves similar to culm leaves, not forming a winter 

 rosette; spikelets all fertile. 



Fruit transversely rugose See 



Fruit not transversely rugose (minutely papillose- 

 roughened in P. millegrana). 



P. cilialissimum. 

 P. obtusum. 



P. pulchellum. 

 P. biglandulare. 



P. stoloniferum. 

 P . frondescens . 



P. polygonatum. 



P. pilosum. 

 P. laxum. 



P. longum. 



Geminata, p. 30. 

 P. hemitomon. 



DlCHANTHE- 

 LIUM, p. 142. 



Maxima, p. 78. 



