580 ORDER CXLII. GRAMlNACEvE. 



30. P. Bos'cn, (Poir.) Stem glabrous, simple. Leaves lanceolate, 

 erect, glabrous ; sheaths bearded at the base and on the margin. Pan- 

 icles short, few-flowered, somewhat pubescent. Glumes nerved. Seed 

 naked. — Car. 



37. P. Walte'ri, (Poir.) Leaves oval-lanceolate, amplexicaul, smooth ; 

 sheaths tomentose, bearded at the base. Panicles sessile, branching. 

 Glumes pubescent ; outer valve oval. — Car. to Vir. 



38. P. commuta'tum, (Schal.) Stem erect, glabrous. Leaves lanceo 

 late, slightly cordate, ciliate at the base, distinctly nerved. Panicle 

 diffuse. Peduncles pubescent. Glume 2- flowered. — 2£. May — July. 

 Dry soils. 2—3 feet. 



39. P. latifo'lium. Stem procumbent, pubescent. Leaves ovate-lan- 

 ceolate, hairy at the throat. Flowers solitary, scattered. Glumes 2- 

 flowered, perfect and sterile, pubescent. Paleai of the perfect flowers 

 larger than those of the sterile ones. — 2T.. Through the summer. 

 Dry, 6hady soils. Common. 12 — 15 inches. 



Genus XI.— ROTTBCEL'LIA. L. 

 (In honor of C. F. Kottboell, a Danish botanist.) 



Flowers in one-sided spikes. Glumes 1 — 2-flowered, the 

 flowers sterile and perfect. 



1. R. dimidia'ta, (Mich.) (Stenotaphrum Americanum, Schra.) 

 Stein creeping, branching, glabrous. Leaves glabrous, sometimes op- 

 posite, perennial ; spikes terminal, flat. Glumes unequal, the exterior 

 shortest. Paleai lanceolate, the exterior longest. — 2£. Through the 

 summer. On the sea-coast. 



Genus XII.— OPLIS'MENUS. Beauv. 

 (From the Greek oplismos, armor.) 



Spikelets 2 -flowered or more; inferior flowers staminate or 

 neutral ; superior flowers perfect. Glumes 2, unequal, concave ; 

 staminate flowers with two paleas, the lower one awned. Sta- 

 mens 3. Perfect flowers ; palese 2, the inferior acuminate, 

 mucronate. Styles 2. 



1. O. seta'rius, (Rcem.) (Panicum hirtellum, Ell.) Stem procum- 

 bent, creeping, sometimes assurgent, hairy at the joints. Leaves undu- 

 late, scabrous, slightly hairy, contracted at the base, throat, and mar- 

 gin of the sheath ; spikes compound ; spikelets 5 — 8-flowered ; rachis 

 angled, villous. Glumes 1 -flowered, with purple awns. — 2f. Aug — 

 Oct. Rich, dry soils. 



2. 0. crus-gal'li, (Kunth.) {Panicum crus-galli, L.) Stem erect, 

 terete, glabrous. Leaves long, scabrous. Flowers on spikes, forming a 

 terminal panicle ; rachis angled, hairy. Glumes 2-flowered, one per- 

 fect, the other sterile ; exterior glume with a long awn ; the interior 

 one flat, awned ; the accessory glume very small. Paleai pubescent. — 

 0. Aug. — Sept. Cultivated grounds. 2 — 4 feet. 



The glumes of this species are not always awned, and the awns vary very much in 

 length. 



