MANUAL OF THE GRASSES OF THE UNITED STATES 609 



First glume much shorter than the sterile lemma. 

 Fruit transversely rugose. 



Nodes glabrous 1. Gem 



Nodes bearded 2. Purpurascentj \. 



Fruit not rugose 15. Hemitoma. 



2b. Spikelets in open or sometimes contracted or congested panicles (some- 

 what 1-sided in Agrostoidia). 



Fruit transversely rugose (obscurely so in P. -plenum) 7. Maxima. 



Fruit not transversely rugose. 



Spikelets villous. .1 13. Urvilleaxa. 



Spikelets glabrous. 



Sterile palea enlarged and indurate at maturity, expanding the spikelet. 

 Blades scarcely wider than their sheaths; spikelets about 2.3 mm 

 long, borne toward the ends of the few slender branches. 1 1 . Laxa. 

 Sterile palea, if present, not enlarged. 



Plants with conspicuous creeping scaly rhizomes. 



Spikelets long-pediceled, not secund, arranged in an open or con- 

 tracted panicle 8. Virgata. 



Spikelets short-pediceled, more or less secund along the nearly 



simple panicle branches 10. Agrostoidia. 



Plants without creeping scaly rhizomes. 



Panicles narrow and few-flowered; culms erect and wiry. Blades 



drying involute 9. Texera. 



Panicles open or contracted, many-flowered. 



Spikelets short-pediceled along the nearly simple panicle 



branches 10. Agrostoidia. 



Spikelets long-pediceled, the panicle open 6. Diffusa. 



1. Geminata 



Spikelets 3 mm long; glumes and sterile lemma papery. _ 112. P. paludivagim. 

 Spikelets not more than 2.4 mm long; glumes and sterile lemma not papery. 



111. P. GEMIXATUM. 

 2. Purpurascentia 



A single species 113. P. purpfrascens. 



3. Fasciculata 



Spikelets 5 to 6 mm long 118. P. texaxum. 



Spikelets 2 to 4 mm long. 



Spikelets strongly reticulate-veined, 2 to 3 mm long; glabrous. 



115. P. fasciculatum. 

 Spikelets scarcely reticulate-veined or only near apex. 



Spikelets not more than 2 mm long, glabrous 114. P. reptaxs. 



Spikelets more than 3 mm long, pubescent. 



Rachis scabrous but not bristly 116. P. adspersum. 



Rachis bristly-hirsute 117. P. arizoxicum. 



4. Dich.otomif.or a 



Sheaths glabrous 119. P. dichotomiflorfm. 



Sheaths papillose-hispid 120. P. bartowexse. 



5. Capillaria 



Panicles drooping; spikelets 4.5 to 5 mm long 130. P. miliacefm. 



Panicles erect; spikelets not more than 4 mm long. 

 Panicles more than half the length of the entire plant. 



Panicles narrow, usually less than half as broad as long 121. P. flexile. 



Panicles as broad as long. 



Fruit without scar at base 125. P. capillare. 



Fruit with a lunate scar at base 126. P. hillmaxi. 



Panicles not more than one-third the entire height of the plant. 



Spikelets not more than 2 mm long, acute but not long-acuminate (see also 

 P. hirsutum). 

 Culms stout; blades about 1 cm wide; spikelets turgid. 



122. P. gattingeri. 



