150 



CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Blades lanceolate ; first glume not more than one- 

 third as long as the spikelet. 

 Culms crisp-puberulent; blades rarely over 

 1 cjp.. wide; spikelets about 2.5 mm. 



long 183 



Culms glabrous or obscurely puberulent; 

 blades usually 1.5 cm. or more wide; 



spikelets 2.7 to 3 mm. long 184 



Spikelets not over 2.3 mm. long; blades not cordate, usu- 

 ally less than 1 cm. wide. 

 Blades conspicuously ciliate, soft and las, crowded 



at the base 88 



Blades not ciliate or so only at base, not crowded 

 at the base of the culm. 

 Blades not over 6 mm. wide; plants not branch- 

 ing or rarely branching from near the 



base 



Blades 7 mm. or more wide; plants branching 

 from middle and upper nodes. 

 Primary blades spreading; panicle purplish; 



fruit exposed at summit 107, 



Primary blades erect; panicle green; fruit 



covered 108. 



Spikelets not over 1.7 mm. long. 



Culms crisp-puberulent; spikelets turgid 147 



Culms glabrous. 



Blades white-margined, firm. 



Blades puberulent beneath, often above 152 



Blades glabrous. 



Uppermost blades much reduced; culms 

 branching from lower nodes only, the 

 branches repeatedly branching 153 



Uppermost blades about as long as the others ; 

 culms bearing short branches from 



middle and upper nodes 154, 



Blades not white-margined or very obscurely so (or 

 if white margin is evident, spikelets only 1.1 

 mm. long). 

 Culms branching only at base; plants soft, light 



green 158 



Culms branching at the nodes. 



Spikelets 1.1 mm. long; winter blades bluish 



green, not glossy 156 



Spikelets 1.3 to 1.5 mm. long. 



Blades involute, falcate, with long stiff 

 hairs on margin near base; plants 



stiff and wiry 162. 



Blades not involute or at tip only, not 

 falcate. 

 Plants bright green; winter blades 



conspicuous, glossy green. . .155. 

 Plants olive; winter blades not con- 

 spicuous nor glossy 157. 



P. commutatum. 



P. dliatum. 



85. P. iverneri. 



P. clutei. 



P. boreale. 



P. columbianum. 



P. tenue. 



P. alhomargina- 

 tum. 



P. trifolium. 



P. vernale. 

 P. concinnius. 



P. breve. 



P.flavovirens. 

 P. ensifolium. 



