146 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Spikelets scarcely more than 3 mm. long. 

 Spikelets turgid, blunt; blades mostly less 



than 1 cm. wide 170. P. helleri. 



Spikelets not turgid; blades more than 1 cm. 

 wide. 

 Panicle narrow, branches ascending; spike- 

 lets on long stiff pedicels 100. P. calliphyllum. 



Panicle as broad as long, branches spreading. 

 Plants glaucous; basal blades conspicu- 

 ously ciliate 185. P. mutabile. 



Plants not glaucous; basal blades not cili- 

 ate, or at the base only. 

 Culms erect, or autumnal form leaning; 

 blades symmetrical, broadly cor- 

 date 184. P. commutatum. 



Culms decumbent; blades usually un- 

 symmetrical and falcate; narrowed 



to the scarcely cordate base 186. P. joorii. 



Sheaths pubescent. 

 Pubescence ascending or appressed. 



Spikelets 3 to 3.2 mm. long; first glume conspicu- 

 ously remote 142. P. malacon. 



Spikelets 3.5 to 4 mm. long; first glume not 



remote 172. P. oligosanthes . 



Pubescence spreading, sometimes sparse. 

 Plants robust, about 1 meter high; blades usually 



2 cm. or more wide 189. P. clandestinum. 



Plants rarely more than 50 cm. high; blades 

 rarely over 1.5 cm. wide. 

 Panicles about as wide as long; blades ascend- 

 ing or spreading. 

 Spikelets attenuate at base, 3.5 to 4 mm. 



long See Pedicellata 



Spikelets not attenuate at base, not over 3.3 (p. 292). 



mm. long. 

 Spikelets 3.2 to 3.3 mm. long, blades firm; 

 sheaths, or some of them, more or less 



hispid 171. P. scribnerianum . 



Spikelets not over 3 mm. long; blades 

 rather thin; sheaths, or some of them, 



glabrous or sparsely hispid 170. P. helleri. 



Panicles narrow, branches erect (sometimes 

 ascending in P. wilcoxianum) , or spreading 

 at anthesis only; blades erect. 

 Spikelets not over 3 mm. long; blades not 



over 6 mm. wide 168. P. wilcoxianum. 



Spikelets 3.7 to 4 mm. long; blades 8 to 20 

 mm. wide. 



Blades papillose-hispid 174. P. leibergii. 



Blades glabrous on both surfaces 175. P. xanthophysum. 



Spikelets less than 3 mm. long. 

 Blades elongated, not over 5 mm. wide; secondary pani- 

 cles at the base only or wanting. 



