292 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



If 



Figure 394. — Trisetum pennsylvanicum. Panicle, X 1; 

 glumes and florets, X 5. (Heller 4800, Pa.) 



long, 2-flowered, the long rachilla 

 internodes slightly hairy; glumes 

 mostly 4 to 5 mm. long, acute, the 

 second wider; lemmas acuminate, the 

 first usually awnless, the second 

 awned below the 2 setaceous teeth, 

 the awn horizontally spreading, 4 to 

 5 mm. long. % — Swamps and 

 wet places, Massachusetts to Ohio 

 and West Virginia, south on the 

 Coastal Plain to Florida and west 

 to Tennessee and Louisiana. 



10. Trisetum interruptum Buckl. 

 (Fig. 395.) Annual; culms tufted, 

 sometimes branching, erect or spread- 

 ing, 10 to 40 cm. tall; sheaths often 

 scabrous or pubescent; blades flat, 

 sometimes pubescent, 1 to 4 mm. 



Figure 395. — Trisetum interruptum. Panicle, 

 glumes and floret, X o. (Jermy, Tex.) 



X 1; 



wide, mostly 3 to 10 cm. long; pan- 

 icle narrow, interrupted, from slender 

 to rather dense but scarcely spike- 

 like, 5 to 12 cm. long, sometimes 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. 



58. DESCHAMPSIA Beauv. Hairgrass 



Spikelets 2-flowered, disarticulating above the glumes and between the 

 florets, the hairy rachilla prolonged beyond the upper floret and sometimes 

 bearing a reduced floret; glumes about equal, acute or acutish, membranaceous; 

 lemmas thin, truncate and 2- to 4-toothed at summit, bearded at base, bearing 

 a slender awn from or below the middle, the awn straight, bent or twisted. 

 Low or moderately tall annuals or usually perennials, with shining pale or 

 purplish spikelets in narrow or open panicles. Standard species, Deschampsia 

 caespitosa. Included in Air a by some authors. Named for Deschamps. 



Deschampsia caespitosa is often the dominant grass in mountain meadows, 

 where it furnishes excellent forage. 



Plants annual; foliage very scant 1. D. danthoxioides. 



Plants perennial; foliage not scant, one-third to half the entire length of the culm. 

 Panicle narrow, the distant branches appressed. 



Glumes 4 to 6 mm. long; lemma smooth, not deepl} T toothed 2. D. eloxgata. 



Glumes 7 mm. long; lemma scaberulous, deeply toothed or lacerate. 



3. D. COXGESTIFORMIS. 



Panicle open or contracted, if narrow, not more than one-fourth the length of the culm. 

 Blades thin, flat; glumes exceeding the florets 4. D. atropurpurea. 



