138 



Agrostideae 



Stipa 



50 



Map 240 



Stipa avenacea L. 



50 



Map 241 



Stipa comata Trin.& Rupr. 



84-209. STIPA L. Needlegrass 

 [Hitchcock. The North American species of Stipa. Contr. U. S. Nation. 

 Herb. 24: 215-289. 1925.] 



Glumes about 10 mm long h S. avenacea. 



Glumes about 15-40 mm long. 



Lemmas 8-12 mm long 2. S. comata. 



Lemmas 15-22 mm long 3. S. spartea. 



1. Stipa avenacea L. Blackseed Needlegrass. Map 240. Local in 

 dry, sandy soil in a few of our northern counties. 



Mass. to Mich., southw. to Fla. and Tex., mostly on the Coastal Plain. 



2. Stipa comata Trin. & Rupr. Needle-and-thread. Map 241. This 

 species is known only from a high gravelly hill on the northeast side of 

 Diamond Lake, Noble County. 



Ind. and Mich, to Yukon Territory, southw. to Tex. and Calif. 



3. Stipa spartea Trin. Porcupine Grass. Map 242. Local to infre- 

 quent or frequent on open sand knolls, sand ridges, and dunes, or rarely 

 on open gravelly places in the northwestern part of the state. 



Ont, to B. C, southw. to Pa., Ind., Kans., and N. Mex. 



85-208. ARISTIDA L. Three-awn Grass 

 [Hitchcock. North American species of Aristida. Contr. U. S. Nation. 

 Herb. 22 : 517-586. 1924. Henrard. A critical revision of the genus Aristida. 

 vii+701p. 1928. Supplement: 702-747. 1933. Rijks Herbarium. Leiden.] 



Awns of lemma united into a column, 10-15 mm long, articulated with the lemma. 



1 . A . tuberculosa. 



Awns of lemma not united into a column and not articulated with the lemma. 

 Lemmas (exclusive of awns) less than 12 mm long. 



Central awn of lemma coiled at the base at maturity; lateral awns rarely more 



than 1.5 mm long 2. A. dichotoma. 



Central awn of lemma not coiled at the base, but abruptly bent outward, usually 

 to a 45-90 degree angle, sometimes with a slight twist at the base; lateral 

 awns usually more than 1.5 mm long. 



