*212 POACE.^. 



Prodr. Fl. Pemv. 2 (1794), Stre]}tac]me E. Br. Prodr. 1:174 

 (1810). Aclinatherum Beauv. Agrost. 19 (1812). Lasiagrostis 

 Link, Hort. Berol. 1 : 99 (1827). Pristella Bertol. Fl. It. 1 : 690 

 (1833). MacrocMoa Kiinth, Eev. Gram. 1:58 (1830). Ortho- 

 raphium Nees, Proc. Linn. Soc. 1:94 (1841). Ptilagr'ostis 

 Griseb. in Led. Fl. Ross. 4:447 (1853). 



Spikelets 1-flowered, on slender spreading pedicels or nearly 

 sessile in a terminal panicle, racliilla articulate above the empty 

 glumes. The two empty glumes persistent, membranjous, keeled, 

 iinawned or rarely v/ith a slender awn; the floral ghime narrow, 

 rigid, rolled around tlie flower, usually with a curved sliarp-pointed 

 hairy callus at the base, and a terminal undivided bent awn spirally 

 twisted below the bend, sometimes with a tooth on each side the 

 base of the awn, the awn tardily separating by a joint or rarely 

 persistent. Palea enclosed by the floral glume, 2-nerved; lodicules 

 often 3 and large. Stamens 3 ; anthers often tipped with a tuft of 

 short hairs. The awn by twisting and untwisting often buries the 

 fruit in the soil. 



Tufted, usually tall grasses, the narrow leaf -blades often involute 

 or convolute. There are about 100 species widely dispersed over 

 the tropical and temperate regions of both hemispheres. 



Stipa is strongly cliaracterized as to the great majority of its spe- 

 cies by the narrow rather hard fruiting glumes, carrying oil a 

 rather long or obconical internode of the rachilla or callus, by the 

 long undivided awn more or less articulate on the glumes and 

 usually twisted at the base, and by the presence of the lodicules; 

 but there are numerous exceptions to one or more of these charac- 

 ters. 'J'he internode of the rachilla varies much in length and 

 shape; the articulation and twist of the awn gradually disappear in 

 some species. The genus is not very clearly divisible into sections. 

 There are generic names which have been proposed for certain 

 species of Stipa and now reduced to synonyms. 



Stipa is closely allied to Ori/zopsis Michx. and more remotely to 

 Aristida L. and Muldenbergia Schreb. 



A. Awn plumose, hairs over 1 mm. long (a) 



a. Awn 10-15 cm. long 1 



