GRAMINEAE (GRASS FAMILY) 99 



glabrous, or the upper surface of the leaf-blades (1-2 dm. long) with a few hairs ; 

 racemes 2-3, 3-5 cm. long ; spikelets .about 2.5 mm. long. Sandy soil, Md. to 

 Fla. and Tex. FIG. 57. Var. AUSTRA.LE Nash. Leaves hairy 

 on the upper surface, sheaths hirsute on the margin. Va. to 

 Fla. and Miss. 



12. P. angustifblium Le Conte. Culms erect or spreading, 

 glabrous, averaging taller than the preceding ; sheaths glabrous 

 or somewhat pilose, especially on the margin ; blades elongated 

 (2-4 dm.), often sparingly pilose on upper surface; racemes 3-5, 

 longer than in the preceding, 6-10 cm. long, spreading. Sandy 

 soil, Md. to Fla., Kan., and Tex. 



13. P. plenipilum Nash. Resembles P. laeve ; but usually 

 taller (5-10 dm.), erect or spreading; and pilose on sheaths 



and blades; racemes 2-4, 4-8 cm. long. (P. praelongum 57. p.iaevex%. 

 Nash.) Fields and open ground, N. J. to Fla., Ala., and Mo. Spikelets x2y 2 . 



14. P. circulare Nash. Culms 5-10 dm. high ; sheaths 



sparsely papillose-hirsute with ascending hairs; blades 2-3 dm, long, 5-8 mm. 

 wide, sparsely hirsute on the upper surface, usually glabrous on the lower ; 

 racemes 2-4, erect or ascending, 6-10 cm. long ; spikelets orbicular, about 3 mm. 

 long. Open moist ground, N. Y. and Mo., southw. 



15. P. floridanum Michx. Culms robust, 1-2 m. high, from a stout scaly 

 rootstock, glabrous ; sheaths hirsute ; blades 3-6 dm. long, 6-10 mm. wide, 

 hirsute on both surfaces; racemes usually 2-4, stout, erect or ascending, 7-12 

 cm. long; spikelets about 4 mm. long. Low ground, Va. to Fla. and Tex. 

 Var. GLABRATUM Engelm. Glabrous and often glaucous ; racemes often 4-7. 

 (P. arundinaceum Poir.) Del. to s. Kan., and southw. 



16. P. diff6rme Le Conte. Similar to the preceding, less robust, glaucous ; 

 culms 5-10 dm. high, leafy at the base ; sheaths often papillose-hirsute near the 

 summit; blades 12-15 cm. long, 6-10 mm. wide (the uppermost much reduced), 

 glabrous or sparsely hirsute ; racemes 2-3 (rarely 4), ascending, 3.5-8 cm. long; 

 spikelets 3-3.5 mm. long. Low sandy ground, N. J. to Fla. and Tex. 



a a. Spikelets in pairs, appearing ^-seriate; sterile lemma 5-nerved', culms 

 usually geniculate and rooting at the lower nodes. 



17. P. laeviglume Scribn. Culms stout, 5-15 dm. high, nodes pubescent; 

 sheaths usually pilose on the scarious margin, otherwise glabrous ; blades 1-3 

 dm. long, 1-1.5 cm. wide, glabrous or with a few hairs at base ; racemes 4-8, 

 3-10 cm. long; spikelets 3 mm. long, obovate, stramineous. Moist fields and 

 wood-borders, Md. and Ky. to N. C. and Tex. Sept., Oct. 



18. P. Boscianum Fliigge. Culms stout, 5-12 dm. high ; sheaths lax, gla- 

 brous, or the lower pubescent; blades 1.5-4.5 dm. long, 6-12 mm. wide, gla- 

 brous or hirsute near base ; racemes numerous, 2-6 cm. long, with a winged 

 rhachis 2 mm. wide ; spikelets 2 mm. long ; glume and sterile lemma brownish ; 

 fruit dark brown. Low woodlands, and along ditches, Va. to Fla. and Tex. 

 Aug., Sept. 



= = Spikelets acute, ciliate. 



19. P. dilatatum Poir. Culms stout, 5-17 dm. high, growing in clumps ; 

 glabrous throughout except the densely crowded spikelets; leaves elongated, 

 4-10 mm. wide; racemes 2-10, 5-10 cm. long, somewhat spreading; spikelets 

 3 mm. long, ovate ; glume and sterile lemma long-ciliate. In meadows, waste 

 ground, and along ditches, Va. to Fla. and Tex. 



-- 1- Racemes a pair at the summit of the culm. 



20. P. distichum L. Creeping and rooting at the nodes, with ascending culms, 

 1-6 dm. high ; leaves short, usually crowded, sometimes sparsely hairy on the 

 margins; racemes 3-5 cm. long; spikelets singly disposed, 2.5-3 mm. long, 

 ovate, acute, sparsely pubescent ; first glume occasionally present. (Digitaria 

 paspalodcs Michx.) Ditches and muddy or sandy shores, Va. to Fla., and 

 westw. June-Oct. 



