284 CONTRIBUTIOiSrS FROM THE NATIONAL HEEBAEIUM. 



9. CINNA L. 



1. Cinna latifolia (TrcAdr.) Griseb. Reedgeass. Common at low and middle 

 altitudes, in moist woods or meadows. B. €. to Utah, N. C, and Newf.; also in 

 Eur.— Plants perennial, with simple erect culms, 1 meter or more tall, flat blades 

 1 to 1.5 cm. wide, and handsome drooping panicles 20 to 30 cm. long, the spikelets 

 3 to 4 mm. long, falling entire. 



10. AGROSTIS L. Bentgrass. 



Plants perennial, with simple culms, flat blades, and open or contracted panicles 

 of V-shaped spikelets, 2 to 4 mm. long, the glumes persistent after the fall of the 

 florets. 



Floret nearly equaling the glumes. Palea developed 1. A. thurheriana. 



Floret noticeably shorter than the glumes. 



Plants producing running rootstocks; palea well developed .... 2. A. palustris. 

 Plants without rootstocks; palea obsolete. 



Panicle dense, its branches verticillate, with short branchlets spikelet-bearing 



to the base in their axils 3. A. exarata. 



Panicle loose and open, the branches naked at the base. 

 Panicle very diffuse, the lower branches commonly 10 cm. or more long. 



4. A. hiemalis. 

 Panicle open but not diffuse, the lower branches rarely over 5 cm. long. 



4a. A. hiemalis geminata. 



1. Agrostis thurberiana Hitchc. At middle altitudes and above timber line, in 

 moist soil. B. C. to Calif., Utah, and Mont. — Plants tufted, rather lax, the delicate 

 culms 20 to 40 cm. tall, the soft blades mostly clustered at the base; panicles 5 to 8 

 cm. long, loosely flowered, the branches and branchlets flexuous, divaricate. 



2. Agrostis palustris Huds. Redtop. Common at low altitudes, in wet or moist 

 8oil,ofteniD sphagnum bogs. Widely distributed in N. Amer., partly or wholly natu- 

 ralized; often cultivated as a meadow or pasture grass; also in Eiu". (A. alba of 

 American authors.) — Plants relatively stout the culm^ mostly 50 cm. or more 

 tall: blades rough, 3 to 6 mm. wide; panicle pyiamidal, mostly purple and 10 to 

 20 cm. long, the rather closely flowered branches in distant fascicles on the main 

 axis , the branchlets spreading in flower but contracted at maturity. 



3. Agrostis exarata Trin. Chiefly at low and middle altitudes, but sometimes 

 about timber line, in meadows or moist woods or along streams. Alaska to Calif., 

 N. Mex., and Nebr.; also in Siberia. {A. grandis Trin.; A. asperifolia Trin.) — Plants 

 tufted, often rather stout, 30 to 75 cm. tall; blades rough, 2 to 5 mm. wide; panicle 

 yellowish green, narrow, 10 to 20 cm. long, the short, densely flowered branches 

 crowded in whorls, the lower distant, the upper close together; glumes long-pointed. 



Plants at high altitudes are often low and delicate, Avith less densely flowered 

 panicles. 



4. Agrostis hiemalis (Walt.) B. S. P. Tickle grass. Common nearly everywhere 

 at low and middle altitudes, in moist woods and thickets or in meadows. Alaska to 

 Mex., Fla., and Lab. — Plants tufted, leafy at the base, 30 to 50 cm. tall; blades 

 mostly less than 2 mm. wide; culms slender, brittle; panicles often nearly half the 

 entire height of the plant and about as broad as long, the few capillary branches 

 widely spreading, spikelet-bearing toward the ends only. 



At maturity the panicles break away and roll before the wind, scattering the seed. 



4a. Agrostis hiemalis geminata (Trin.) Hitchc. Granite Park, on moist rocky 

 slopes, and doubtless elsewhere. Alaska to Calif, and Colo. {A. geminata Trin.) — 

 Plants mostly not over 20 cm. tall; panicles less diffuse than in the species, the 

 lemmas often awned from the back. 



