Part 3, 1915] POACEAB 



209 



Plants lax, soft- velvety throughout; spikelets not more than 3 mm. 



long. _ 181. P. malacophyllum 



Plants stiff, the pubescence harsh; spikelets about 4 mm. long. 185. P. Ravenelii. 



Nodes not bearded (or but obscurely so in P. Wilcoxianum) ; leaf -blades 

 not velvety. 

 Panicle narrow, the branches erect, or spreading only at anthesis; 

 leaf -blades erect. 

 Spikelets not more than 3 mm. long; leaf -blades not more than 6 



mm. wide. 180. P. Wilcoxianum, 



Spikelets 3.7-4 mm. long; leaf -blades 8-20 mm. wide. 



Blades papillose-hispid. 186. P. Leibergii. 



Blades glabrous on both surfaces. 187. P. xanthophysum. 



Panicle about as wide as long. 



Spikelets broadly obovate, turgid, blunt; plants green, the pubes- 

 cence, if present, not appressed. 

 Leaf -blades erect, not more than 6 mm. wide; plants copiously 



hirsute throughout. 180. P. Wilcoxianum. 



Iyeaf -blades ascending or spreading, rarely less than 8 mm. wide, 

 usually wider; plants not hirsute throughout. 

 Spikelets not more than 3 mm. long; leaf -blades rather thin; 



sheaths, or some of them, glabrous or sparsely hispid. 182. P. Helleri. 

 Spikelets 3.2-3.3 mm. long; leaf -blades firm; sheaths, or 



some of them, more or less hispid. 183. P. Scribnerianum. 



Spikelets narrowly obovate, subacute; plants olivaceous, ap- 



pressed-pubescent. 184. P. oligosanthes. 



XXXVI. Scoparia. 



Pubescence soft-villous or velvety; spikelets abruptly pointed. 



Vernal culms erect or ascending; plants velvety throughout; spike- 

 lets about 2.5 mm. long. 188. P. scoparium. 

 Vernal tulms decumbent at base; upper leaf -sheaths more or less 



glabrate; spikelets less than 2 mm. long. * 189. P. viscidellum. 



Pubescence when present- not velvety. 



Spikelets elliptic; fruit 2 mm. long. 190. P. aculeatum. 



Spikelets ovate, that is, broadest below the middle; fruit 2 mm. long 

 or less. 

 Leaf -sheaths, or some of them, hispid, rarely glabrous; autumnal 



phase with crowded branchlets. 191. P. scabriusculum. 



Leaf -sheaths glabrous; autumnal phase sparingly branching. 192. P. cryptanthum. 



XXXVII. COMMUTATA. 



Plants glaucous, glabrous ; basal leaf -blades conspicuously ciliate ; vernal 



culms usually solitary. 

 Plants not glaucous. 



Leaf -blades lanceolate. 



Culms crisp-puberulent ; leaf -blades usually rigid, symmetric, 



rarely more than 10 mm. wide; spikelets about 2.5 mm. long. 193. P. Ashei. 

 Culms glabrous or softly puberulent; leaf -blades firm or lax; 

 spikelets 2.7-3.2 mm. long. 

 Culms erect, or in the autumnal phase leaning; leaf -blades 



symmetric, broadly cordate. 194. P. commutatum. 



Culms decumbent ; leaf -blades usually asymmetric and falcate, 



narrowed to the scarcely cordate base. 196. P. Joorii. 



Leaf -blades nearly linear, that is, with parallel margins; first glume 

 about half as long as the spikelet. 

 Primary panicles short-exserted ; leaf -sheaths not mottled. 197. P. equilaterale. 



Primary -panicles long-exserted ; leaf -sheaths mottled with white. 198. P. albomaculatum, 



195. P. mutabile. 



199. P. clandestinum 



XXXVIII. Latifoua. 



Leaf -sheaths, at least the lower and those of the branches, strongly 



papillose -hispid . 

 Leaf -sheaths glabrous or softly villous. 



Nodes glabrous; spikelets 3.4-3.7 mm. long. * 200. P. latifolium. 



Nodes bearded; spikelets 4-4.5 mm. long. 201. P. Boscii. 



XXXIX. PedicEU,aTa. 



Culms erect or leaning; leaf -blades thin, 5-9 cm. long, narrowed toward 



the base. * 202. P. pedicellatutn 



Culms decumbent; leaf -blades thick, not more than 5 cm. long, not 



narrowed toward the base. 203. P. nodatum. 



XL. Cordovensia. 



Plants glabrous or the leaves sparsely pilose. 204. P. cordovense. 



Plants velvety-pubescent. • 205. P. chiriquiense. 



XLI. Obtusa. 



One species. 206. P. obtusum. 



XLH. Grandia. 



One species. 207. P. grande. 



