MANUAL OF THE GRASSES OF THE UNITED STATES 613 



the latest more or less included in the sheaths, the spikelets 

 cleistogamous and perfecting their grains. The species of this 

 subgenus are usually known as dichotomous panicums because 

 they are related to Panicum dichotomum. 



Key to the species irrespective of the groups 



la. Spikelets glabrous. 



2a. Spikelets 3 mm long or more, strongly nerved. 



Spikelets pointed; blades elongate 5. P. depauperatum. 



Spikelets blunt; blades not elongate. 



Spikelets 3.2 to 3.3 mm long; blades firm; sheaths, or some of them, hispid. 



92. P. SCRIBNERIANUM. 



Spikelets not more than 3 mm long; blades rather thin; sheaths glabrous 



or sparsely hispid 91. P. helleri. 



2b. Spikelets less than 3 mm long. 



3a. Second glume and sterile lemma exceeding the fruit and pointed beyond 

 it. Spikelets 2.2 to 2.9 mm long. 



Blades clustered toward the base 24. P. nudicaule. 



Blades not clustered toward the base. 



Sheaths, at least the secondary, hispid 101. P. scabriusculum. 



Sheaths glabrous. 



Blades firm; fruit 1.5 mm long 102. P. cryptanthum. 



Blades thin; fruit nearly 2 mm long 33. P. yadkinense. 



3b. Second glume and sterile lemma not pointed beyond the fruit. 

 4a. Ligule manifest, 1 to 3 mm long. 



Culms rather stout; ligule 2 to 3 mm long; sheaths glabrous. 



38. P. spretum. 

 Culms slender; ligule 1 mm long; sheaths sparsely pilose. 



80. P. CURTIFOLIUM. 



4b. Ligule obsolete. 



5a. Spikelets 1.5 mm or less long. 



Nodes bearded 25. P. microcarpon. 



Nodes not bearded. 



Culms and blades pilose 13. P. strigosum. 



Culms glabrous. 



Blades conspicuously ciliate; plants branching at base only. 



12. P. POLYCAULON. 



Blades not ciliate; plants branching from middle or upper nodes. 

 Vernal culms 50 cm tall or more; spikelets turgid, strongly 

 nerved; autumnal phase erect, with fascicled branches 

 shorter than the primary internodes. 



35. P. CAERULESCENS. 



Vernal culms usually much less than 50 cm tall; autumnal 

 phase spreading or reclining. 

 Spikelets 1.1 to 1.2 mm long. Blades rarely as much as 5 cm 



long 81. P. CHAMAELONCHE. 



Spikelets 1.2 to 1.4 mm long. 



Blades elongate, at least some of them 8 to 10 cm long. 



82. P. GLABRIFOLIUM. 



Blades not more than 3 cm long 78. P. ensifolium. 



5b. Spikelets 2 mm long or more. 



Blades elongate, some of them 20 times as long as wide; spikelets 2.2 

 to 2.8 mm long. 

 Blades erect; branches, when present, from the lower nodes only. 



8. P. WERNERI. 



Blades spreading; branches from upper nodes. 22. P. bicknellii. 

 Blades not elongate, about 10 times as long as wide. 

 Culms soon prostrate, vinelike; branches divaricate. 



Plants bright green; culms lax; spikelets not more than 2.1 mm 



long 36. P. lucidum. 



Plants grayish green; culms stiff; spikelets 2.5 mm long. 



37. P. SPHAGNICOLA. 



