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 sjil, Md. to 

 Fla. and Tex. Fig. 57. Var. australe Nash. Leaves hairy 

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

 Fla. and Miss. 



12. P. angustif51ium 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. \aeve ; 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. laeve x Va- 

 Nash.) — Fields and open ground, N. J. to Fla., Ala., and Mo. Spikelets x2% 



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. glabrA-tum 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\2-lb 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 ^-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 

 im. 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-cilia.te. — In meadows, waste 

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



•^•^- Racemes a pair at the summit of the culm. 



20. P. distichiim 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 

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

 westw. June-Oct. 



