*212 POAC'E.B. 



I'rodr. Fl. Peruv. 2 (1T94). Strvptarhne W. Wv. Prodr. i:i:-4 

 (ISIO). Ac/iiKtf/icnii/i Boiiuv. Agrost. 10 (1812). Lasiufirostis 

 Link, llort. Ik-rol. 1:!)!» (182:). PrusfeUa Jk'rtol. Fl. It. 1 : «{)0 

 (is:5:{). Mavrui'ldoa Kunth, Kev. (iram. 1:68 (1830). Ortho- 

 rdjthium Nei'S, Proc. Linn. Hoc. 1:0-4 (1841). PtilagroKtis 

 (irisi'b. in Led. Fl. IJoss. 4:447 (1853). 



Spikc'lets l-llowcrt'd, on slender spreading pedicels or nearly 

 sessile iu a terminal panicle, raichilla articulate above the empty 

 glnmes. The two empty glumes persistent, membranous, keeled, 

 unawned or rarely with a slender awn; the floral glume narrow, 

 rigid, rolled around the tlowiT. usually with a curved sharp-pointed 

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

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

 base of the awn, the awn tardily se})arating 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 s[)e('ies widely dispersed over 

 the tropical and temperate regions of both hemispheres. 



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

 cies by the narrow rather hard fruiting glumes, carrying otf 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. The internode of the rachilla varies much in length and 

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

 some species. The genus is not very clearly divisil)le into sections. 

 There are generic names wliicli have been projjosed for certain 

 species of Stipa and now reduced to synonyms. 



Stipa is closely allied to Or t/zop.si,s' Michx. and more remotely to 

 Aristida L. and Mn/ih'>it)erf/ia Hchreb. 



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



a. Awu 10-15 cm. long 1 



