AUROSTIDE.E. 19'S 



There are over 100 species widel}' spread over the tropieiil and 

 temperate regions of the New and tlie Old World. 



The genus is nearly related to Stipu, though separated from it 

 hy having triple awns. 



With few exceptions it is most leadily recognized by the long 

 fine three-branched awns, the lateral ones opposite and spreading. 

 The genus is divided into three fairly marked sections, wliich by 

 some have been raised to the rank of genera. 



1. Arthrathemm (Beauv., as a genus). — Here the awn is decid- 

 edly articulate on the glume, tlie three consolidated below and. much 

 twisted above the articulation below the branches, the floral glume 

 much shorter than the lower empty glumes, instead of exceeding 

 them as in Chwiaria. 



2. Chwtaria (Beauv., as a genus). — The floral glume is contin- 

 uous \viil\ the awn without any articulation, and is neither quite 

 awnlike in ^ decidedly twisted below the three subequal branches. 

 Amongst its species, Curtopoyon was proposed as a genus, in Avhich 

 the lateral branches of the awn are short and erect. Orfachne 

 (Nees, as a genus), Slreptachne II. B. K., are two other old generic 

 names. 



3. Stipayrostis (Nees, as a genus). — The awn is articulate on 

 the glume jis in AHhratherum, but scarcely twisted, and above the 

 branches elegantly plumose. /ScJiisfac/itie was once proposed as a 

 genus, in which the central awn above is plumose, the lateral ones 

 short and glabrous. 



Not represented by species in our flora. 



A. Arthrathenim. 



a. Floral glume 10 mm. or more in length to the joint, (b) 

 b. Empty glumes 10-15 mm. long, })aniele few-flowered. 1 

 b. Empty glumes 15-17 mm. long, panicle larger. . 'l 



a. Floral glume 8 mm. or less in length to the joint, the twist- 

 ed beak 15 mm. or more in length (b) 



b. Second empty glume 10 mm. long 3 



b. Second empty glumes 13-18 mm. long, variety of 3 



B. Clurlai'ia, 



a. Awns united, solid and twisted at the base. 2 or more em. 

 long 4 



