MANUAL OF THE GRASSES OF THE UNITED STATES 



287 



Figure 564.— Trisetum pennsylvanicum. Pan- 

 icle, X 1; glumes and florets, X 5. (Heller 

 4S00, Pa.) 



with purplish panicles and erect awns only 2 to 3 mm long, known 

 from a single collection near Silverton, Colo., has been differentiated 

 as T. montanum var. shearii Louis-Marie. 



8. Trisetum flavescens (L.) Beauv. (Fig. 563.) Resembling 

 T. canescens; sheaths glabrous or the lower sparsely pilose; panicle 

 usually yellowish, many-flowered, somewhat condensed; spikelets 

 mostly 3- or 4-flowered; lemmas 4 

 to 6 mm long. 91 — Waste places, 

 Vermont, Xew York, Missouri, Colo- 

 rado, Washington, California, and 

 probably other States; introduced 

 from Europe. 



Trisetum aureum (Ten.) Ten. 

 Annual; culms 10 to 20 cm tall; 

 panicle ovate, contracted, 2 to 3 

 cm long; spikelets 3 mm long; awns 

 2 to 3 mm long. o — Ballast, 

 Camden, N. J.; Europe. 



9. Trisetum pennsylvanicum (L.) 

 Beauv. (Fig. 564.) Culms slen- 

 der, weak, usually subgeniculate at 

 base, 50 to 100 cm tall; sheaths 

 glabrous or rarely scabrous; blades 

 flat, scabrous, 2 to 5 mm wide; pan- 

 icle narrow, loose, nodding, 10 to 20 cm long; pedicels disarticulating 

 about the middle or toward the base; spikelets 5 to 7 mm long, 

 2-flowered, the long rachilla joints slightly hairy; glumes mostly 



4 to 5 mm long, acute, the second wider; lem- 

 mas acuminate, the first usually awnless, the 

 second awned below the 2 setaceous teeth, 

 the awn horizontally spread- 

 ing, 4 to 5 mm long. % — 

 Swamps and wet places, Mas- 

 sachusetts to Ohio, south on 

 the Coastal Plain to Florida 

 and west to Tennessee and 

 Louisiana (fig. 565). 



10. Trisetum interruptum Buckl. (Fig. 566.) 

 Annual; culms tufted, sometimes branching, erect 

 or spreading, 10 to 40 cm tall; sheaths often sca- 

 brous or pubescent; blades flat, sometimes pubes- 

 cent, 1 to 4 mm wide, mostly 3 to 10 cm long; 

 panicle narrow, interrupted, from slender to rather 

 dense but scarcely spikelike, 5 to 12 cm long, some- 

 times with smaller axillary panicles; pedicels dis- 

 articulating a short distance below the summit; 

 spikelets about 5 mm long, 2-flowered, the second 

 floret sometimes rudimentary; glumes about equal 

 in length, acute, 4 to 5 mm long, the first 3-nerved, 

 the second a little broader, 5-nerved; lemmas acuminate with 2 

 setaceous teeth, the awns attached above the middle, flexuous, 4 to 

 8 mm long, that of the first lemma often shorter and straight, o 

 —Open dry ground, Texas to Colorado and Arizona (fig. 567). 



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Figube 565.— Distribution of 

 Trisetum pennsylvanicum. 



Figube 566— Trisetum 

 interruptum. Panicle, 

 X 1; glumes and floret, 

 X 5. (Jermy, Tex.) 



