MANUAL OF THE GRASSES OF THE UNITED STATES 



acuminate, 1 -nerved, 0.5 to 2 mm. 

 long, the second broad, 3-nerved, 3 

 to 4 mm. long, occasionally reduced; 

 lemma 5 to 6 mm. long, the teeth 

 setaceous, the hairs of the callus 0.5 

 to 1 mm. long, of the rachilla as 

 much as 2 mm. long, the awns slen- 

 der, curved, flexuous or loosely spiral, 

 mostly 5 to 10 mm. long, attached 

 1 to 2 mm. below tip. % — Moist 

 woods, Alberta to southeastern Alas- 

 ka, south to western Montana and 

 northern California. 



5. Trisetum spicatum (L.) Richt. 

 Spike trisetum. (Fig. 390.) Culms 

 densely tufted, erect, 15 to 50 cm; 

 tall, glabrous to puberulent; sheaths 

 and usually the blades puberulent; 

 panicle dense, usually spikelike, often 

 interrupted at base, pale or often 

 dark purple, 5 to 15 cm. long; spike- 

 lets 4 to 6 mm. long; glumes somewhat 

 unequal in length, glabrous or sca- 

 brous except the keels, or sometimes 

 pilose, the first narrow, acuminate, 

 1-nerved, the second broader, acute, 

 3-nerved; lemmas scaberulous, 5 mm. 

 long, the first longer than the glumes, 

 the teeth setaceous; awn attached 

 about one-third below the tip, 5 to 

 6 mm. long, geniculate, exserted. % 

 — Alpine meadows and slopes, Arctic 

 America, southward to Connecticut, 

 Pennsylvania, northern Michigan and 

 Minnesota, in the mountains to New 

 Mexico and California; also on Roan 

 Mountain, N. C; high mountains 

 through Mexico to the Antarctic 

 regions of South America; Arctic 

 and alpine regions of the Old World. 

 In northern regions the species de- 

 scends to low altitudes. Exceedingly 

 variable; several varieties have been 

 proposed, but the characters used to 

 differentiate them are variable and 

 are not correlated. Two rather more 

 outstanding varieties, both inter- 

 grading with the species are: T. 

 spicatum var. molle (Michx.) Beal, 

 with densely pubescent foliage, and 

 T. spicatum var. congdoni (Scribn. 

 and Merr.) Hitchc, a nearly gla- 

 brous alpine form with slightly larger 

 spikelets. 



289 



Figure 389. — Trisetum cernuum. Panicle, X 1 ; glumes 

 and floret, X 5. (Elmer 1946, Wash.) 



6. Trisetum canescens Buckl. Tall 

 trisetum. (Fig. 391.) Culms erect, 

 or decumbent at base, 60 to 120 cm. 

 tall; sheaths, at least the lower, 

 sparsely to densely and softly re- 

 trorse-pilose, rarely scabrous only; 

 blades fiat, scabrous or canescent, 

 sometimes sparsely pilose, mostly 2 

 to 7 mm. wide; panicle narrow, us- 

 ually loose, sometimes interrupted 

 and spikelike, 10 to 25 cm. long; 

 spikelets about 8 mm. long, 2- or 

 3-flowered, the florets not so distant 

 as in T. cernuum; glumes smooth, 

 except the keel, the first narrow, 

 acuminate, the second broad, acute, 

 3-nerved, 5 to 7 mm. long; lemmas 

 rather firm, scaberulous, the upper 

 exceeding the glumes, 5 to 6 mm. 

 long, the teeth aristate, the callus 

 hairs rather scant, the rachilla hairs 

 copious; awn geniculate, spreading, 

 loosely twisted below, attached one- 

 third below the tip, usually about 12 

 mm. long. % — Mountain mead- 

 ows, moist ravines and along streams, 

 Montana to British Columbia, south 

 to central California. Plants with less 

 pubescent sheaths and looser pan- 

 icles resemble T. cernuum but in that 

 the spikelets are commonly 3-flow- 

 ered, the florets distant. Plants with 

 more velvety foliage and narrow pan- 

 icles with short densely flowered 



