126 



GRAMINEAE (GRASS FAMILY^ 



87 A. tuberculosa. 

 Spikelet x %. 



Mass. to Minn., 



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



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, 



aiV7is 5-10 cm. long. — Y>vy prairies, Minn, south \v. 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^ 



\-\ 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 



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



1.5-3 cm. long, the middle somewhat longer 



than the lateral. — Sandy or gravelly soil, 



and southw. ( W. I.) Fia. 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, '^-Q 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 pme 

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



A. purpurascens. 

 Spikelet x 1. 



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 Bev. 

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



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

 b. Glumes at least one-half as long as the floret e. 



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 \. M. soholifera. 



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



O. Glumes lanceolate, acute to aristate-pointed. 

 Glumes not longer than the lemmas. 



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

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



More or less glomerate 4. M. foUosa. 



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

 tially included 5. 3/. mexicana. 



Glumes much exceeding the awnless lemmas 6. J/, racemosa. 



b. Glumes not more than one-fourth as long as the florets . . . . 7. M. Schreberi. 

 a. Panicle diffuse ; culms simple ; leaves involute S. M. eapillaris. 



§ 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. 

 •i- Glumes broadly ovate, ^-f as long as the floret, which is often conspicuousl'§ 



hairy at base. 

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

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



