GRASSES OF IOWA. 125 



Spikelets i-flowered, terete; the flower falling away at maturity 

 (with the conspicuous, obconical, bearded and often sharp-pointed callus) 

 from the membranaceous, persistent, lower glumes. Fertile glumes coria- 

 ceous, cylindrical-involute, and closely embracing the smaller palet and 

 the cylindrical grain, having a long and twisted or tortuous, simple awn 

 jointed with its apex. Stamens mostly 3. Stigmas plumose. Peren- 

 nials, with narrow, involute leaves and a loose panicle. (Name from 

 the Greek word for tow in allusion to the flaxen appearance of the 

 feathery awns of the original species. In our species the awn is naked.) 



Species about 100 according to Bentham & Hooker and Hackel. 

 Found chiefly in the tropics, generally in savannas, steppes and prairie 

 regions. In southern and central Europe to Russia; Asia, North and 

 South America, Africa and Australia. 



KEY TO THE SPECIES OP STIPA. 



Empty glumes less than 10 mm. long 5. viridula . x 



Empty glumes over 15 mm. long. 



Base of panicle usually included in upper sheath; flowering glume 8-12 



mm. long; awn slender, curled S.comata." 



Panicle wholly exserted, flowering glume 14-24 cm. long; awn stout, 

 bent S. spartea.* 



1. STIPA VIRIDULA. 



Stipa viridula Tr n. Mem. Bull. Sc. Acad. St. Petersb. VI. 2: 39. 

 1836. Beal Grasses N. Am. 2: 221. Watson and Coulter. Gray. Man. Bot. 

 642. 1890. 16th ed.) Nash in Britton and Brown. 111. Fl. 1: 138. /. 310. 1896. 

 Scribner. Bull. U. S. Dept. Agrl. Div. Agros. 17: 134. /. 430 1899. Vasey 

 Contr. U. S. Nat. Herb. 3: 50. in part. 



