GENERA OF GRASSES OF THE UNITED STATES. 45 



narrow panicles of cylindric spikelets, the lemmas pubescent below, is 

 common at lower altitudes in California. Mutton grass (P. fendleri- 

 ana) is important in the Southwest. Little bluegrass (P. sand- 

 bergii), differing from malpais bluegrass in having smooth sheaths, is 

 common at medium altitudes (2,000 to 8,000 feet) throughout the 

 Northwest. 



9. BRIZA L., the quaking grasses. 



Spikelets several-flowered, broad, often cordate, the florets crowded 

 and spreading^ horizontally, the rachifla glabrous, disarticulating 

 above the glumes and between the florets, the uppermost floret re- 

 duced; glumes about equal, broad, papery-chartaceous, with scarious 

 margins; lemmas papery, broad, with scarious, spreading margins, 

 cordate at base, several-nerved, the nerves often obscure, the apex 

 in our species obtuse or acutish ; palea much shorter than the lemma. 



Annual or perennial, low grasses, with erect culms, flat blades, and 

 usually open, showy panicles, the pedicels in our species capillary, 

 allowing the spikelets to vibrate in the wind. Species about 20, the 

 greater number South American. The three species found in the 

 United States are introductions from Europe and occur here as 

 occasional weeds in waste places. 



Type species : Briza media L. 



Briza L., Sp. PI. 70, 1753; Gen. PI., ed. 5, 32. 1754. Linnaeus describes 4 

 species, B. minor, B. media, B. maxima, and B. eragrostis. The first three were 

 familiar to Linnaeus as cultivated plants in the Hortus Cliffortianus, and the 

 second, which is selected as the type species, was described in his flora of Swe- 

 den. The first three species are now retained in Briza, the last is referred to 

 Eragrostis. 



Of the three species found in this country, one, Briza media (fig. 

 14) , is perennial, and two, B. minor and B. maxima, are annual. The 

 spikelets of B. maxima, a species sometimes cultivated for ornament 

 under the name quaking grass, are large and showy, half an inch long, 

 drooping on slender pedicels. Briza minor, with smaller upright 

 spikelets, is rather common on the Pacific coast. 



10. ERAGROSTIS Host. 



Spikelets few to many flowered, the florets usually closely imbri- 

 cate, the rachilla disarticulating above the glumes and between the 

 florets, or continuous, the lemmas deciduous, the paleas persistent; 

 glumes somewhat unequal, shorter than the first lemma, acute or 

 acuminate, 1-nerved, or the second rarely 3-nerved; lemmas acute 

 or acuminate, keeled or rounded on the back, 3-nerved, the nerves 

 usually prominent; palea 2-nerved, the keels sometimes ciliate. 



Annual or perennial grasses of various habit, the inflorescence an 

 open or contracted panicle. Species more than 100, tropical and tem- 

 perate regions ; 33 species in the United States, in all except the cool 

 or mountain regions. 



