MANUAL OF THE GRASSES OF THE UNITED STATES 



35 



Section S. Bromium 

 Panicle contracted, rather dense, the branches erect or ascending. 



Lemmas glabrous 27. B. racemostjs. 



Lemmas pubescent. 



Spikelets compressed; lemmas rather thin and narrow. 26. B. molliformis. 



Spikelets turgid; lemmas rather thick, broader 25. B. mollis. 



Panicle open, the branches spreading. 



Awn short or wanting; lemmas obtuse, inflated (see also short-awned forms of 



B. secalinus) 22. B. brizaeformis. 



Awn well developed. 



Sheaths glabrous 23. B. secalinus. 



Sheaths pubescent. 



Branches of the panicle rather stiffly spreading or drooping, not flexuous; 



awn straight 24. B. commutatus. 



Branches slender, lax or flexuous. 



Panicle 8 to 11 cm (rarely to 15 cm) long; branches and pedicels conspic- 

 uously flexuous or curled; lemmas pubescent. 30. B. arenaritjs. 

 Panicle 15 to 25 cm long (smaller in depauperate specimens), the long 

 branches spreading or drooping, somewhat flexuous but usually not 

 curled; lemmas glabrous or scaberulous. 

 Palea distinctly shorter than its lemma; awn flexuous, somewhat 

 divergent in drying; spikelets rather turgid_ 28. B. japonictjs. 

 Palea about as long as its lemma; awn straight or nearly so in drying; 

 spikelets thinner and flatter, scarcely turgid. 29. B. arvensis. 



Figure b.—Bromus catharticus, X 1. (Peebles, Harrison, and Kearney 1271, Ariz.) 



Section 4- Eubromus 

 Panicle contracted, erect; awn 12 to 20 mm long. 



Culms pubescent below the dense panicle 33. B. rtjbens. 



Culms glabrous below the scarcely dense panicle 34. B. madritensis. 



Panicle open, the branches spreading. 



Second glume usually less than 1 cm long; pedicels capillary, flexuous. 



35. B. TECTORTTM. 



Second glume more than 1 cm long; pedicels sometimes flexuous but not 

 capillary. 



Awn about 2 cm long; first glume 8 mm long 32. B. sterilis. 



Awn 3 to 5 cm long; first glume about 15 mm long 31. B. rigidus. 



Section 5. Ncobromus 

 A single species 36. B trinii. 



Section 1. Cerat6chloa (Beauv.) Griseb. 

 Annuals, biennials, or perennials; spikelets large, distinct!}' com- 

 pressed; glumes and lemmas keeled, rather firm. 



