AGROSTIDE.E. 203 



40-60 cm. high. Sheaths not crowded from the iuternodes; ligule 

 very sliort; bhides 3, flat, 10-18 cm. long. Panicle often on a pedi- 

 cel of its own length, spikelike, interrupted, the appressed rays 

 mostly in couples. Spikelets 8 mm. long to the tips of tlie sub- 

 equal, 1-nerved, empty glumes; floret 4.5 mm. long; the lateral 

 awns 10 mm. long, the central one a third longer. 



New Jersey, J. H. Holmes for Nat. Mus. Vasey says it has 

 been classed with A. (jraciUs, and with forms of A. pvrjntrea, but 

 it is probably Trinius' old species. It much resembles .1. s/n'cfa 

 Michx. 



18. A. Humboldtiana Trin. and Rupr. Mem. Acad. St. Petersb. 

 (VI.) 7:118 (1849). A. divarimta H. B. K. Willd. Enum. 99 

 (1809). ChcBtium divaricata Beauv. Agrost. 30 (1812). 



An erect grass, 30-90 cm. high. Sheaths covering the nodes; 

 blades convolute, rigid, 12-20 cm. long ; ligule ciliate, sliort. Pani- 

 cle often partially included, 20-30 cm. long, narrow or widely 

 spreading; rays mostly in twos below, single above, some of them 

 10-13 cm. long, sparsely flower-bearing along the upper two-fifths. 

 Empty glumes purplish, 1-nerved, equal, or the lower a little the 

 longer, about 12 mm. long, besides a very short awai; florets often 

 scabrid and spotted, 9 mm. long, some of them sterile and shorter; 

 awns erect, the lateral ones about as long as the spikelet, the cen- 

 tral one 2-6 mm. longer; palea 1 mm. long. 



Mexico, Palmer 284, 768; Arizona, Toiimey 784; California, 

 Jones; New Mexico, Vasey. 



New Mexico, Arizona to California. 



19. A. lanata Poir. Encycl. Suppl. 1:453 (1810). Clmtaria 

 gossypina Beauv. Agrost. 30 (1812). Aristida Janosa Mulil. 

 Gram. 174 (1817). 



An erect rather stout perennial, 60-120 cm. high. Sheaths 

 covering the nodes, often woolly; ligule very short; blades 3 or 

 more in number, rough or smooth above, smooth below, rigid, 

 usually becoming involute, 30-60 cm. or more long. Panicle much 

 exserted, 30-60 cm. long, si)ikelike; rays in couples, some of them 

 10-15 cm. long, flower-bearing along the upper two-thirds. Empty 

 glumes with scabrous keels and straight awns, 1-2 mm. long, the 



