126 



GBAMINEAE (GRASS FAMILY) 



8. A. purpurea Nutt. Culms simple, 3 dm. high or less, densely tufted, 

 spreading ; leaves involute and filiform ; ligule pilose ; panicle loose, of rather 

 few slender-pediceled spikelets; glumes 1-nerved, the first 

 about half the length of the second, which is 1.5-2 cm. long, 

 awns 5-10 cm. long. Dry prairies, Minn, southw. and westw. 

 9. A. purpurascens Poir. In small tufts, glabrous, 3-6 dm. 

 high ; culms erect, simple or sparingly branched ; leaves 1-2 dm. 

 long, 1-4 mm. wide, usually involute toward 

 the ends; panicle purplish, very slender, 

 J-i the entire length of the plant, loosely 

 or rather densely flowered ; glumes 10-12 

 mm. long, 1-nerved, scabrous, the first slightly 

 the longer, attenuate-aristate, the second 

 aristate from a bidentate apex ; lemma 

 87. A. tuberculosa. 6-7 mm. long ; awns divergent, not twisted, 

 Spikelet x %. 1.5-3 cm. long, the middle somewhat longer 

 than the lateral. Sandy or gravelly soil, 

 Mass, to Minn., and southw. ( W. I.) FIG. 88. Variable ; a 

 very delicate, apparently annual, form occurs in wet sands 

 and 'drying sloughs in n. Ind. 



10. A. lanbsa Muhl. Culms stout, erect, simple, 6-12 dm. 

 high ; sheaths {at least the lower) woolly ; blades flat, 3-6 dm. 

 long, 3-6 mm. wide ; panicles nearly half the length of the 

 entire plant, narrow, rather loosely flowered, nodding ; glumes 

 subequal, 1-1.4 cm. long, the first slightly the longer, acumi- 

 nate, the second mucronate from a bidentate apex ; lemma 

 spotted, about 1 cm. long ; lateral awns 10 mm. long, the 

 divergent middle awn 1.5-2 cm. long. (A. lanata Poir., not Forsk.) Dry pine 

 barrens, mostly near the coast, Del. to Tex. and I. T. Sept., Oct. 



26. MUHLENBERGIA Schreb. 



Spikelets 1-flowered, in contracted (rarely open) panicles ; a short usually 

 barbate callus below the floret ; glumes thin, often aristate ; lemma narrow, 

 membranaceous, 3-nerved, awned or awnless, inclosing a thin subequal palea ; 

 grain closely enveloped by the lemma. Our species perennial, often with scaly 

 rootstocks, flat or involute leaves and small spikelets. (Dedicated to the Rev. 

 Dr. Henry Muhlenberg, a distinguished American botanist, 1753-1815.) 



a. Panicle more or less contracted, not diffuse ; culms branched ; leaves flat &. 

 &. Glumes at least one -half as long as the floret c. 



c. Glumes broadly ovate, more or less clasping, one-half to two-thirds as 

 long as the floret. 



Spikelets 1.5-2 mm. long; lemmas awnless 1. M. sobolifera. 



Spikelets 3-4 mm. long ; lemmas awned . . ... 2. M. tenuifiora. 

 c. Glumes lanceolate, acute to aristate-pointed. 

 Glumes not longer than the lemmas. 



Panicles linear or filiform, spikelets not crowded . . . . 3. M. sylvatica.. 

 Panicles oblong or cylindrical, long-exserted, spikelets crowded, 



more or less glomerate 4. M. foliosa. 



Panicles ovoid or subpyramidal, numerous, short-exserted or par- 

 tially included 5. M. mexicana. 



A. purpurascens. 

 Spikelet x 1. 



Glumes much exceeding the awnless lemmas 

 b. Glumes not more than one-fourth as long as the florets 

 a. Panicle diffuse ; culms simple ; leaves involute 



6. M. racemosa. 



. 7. M. Schreberi. 



8. M. capillaris. 



1. EUMUHLENBERGIA Dalla Torre & Harms. Panicles contracted or glom- 



erate, on branching culms usually from scaly creeping rootstocks; leaves flat. 

 * Glumes at least \ as long as the floret, scabrous on the keel ; all the species with 



clusters of scaly rootstocks. 

 *- Glumes broadly ovate, ^-f as long as the floret, which is often conspicuously 



hairy at base. 



\. M. sobolifera (Muhl. ) Trin. Culms erect or ascending, sparingly branched, 

 4-8 dm. high, scabrous below the glabrous nodes, leafy toward the summit, 



