580 ORDER CXLII. GRAMINACE^E. 



36. P. Bos'cn, (Poir.) Stem glabrous, simple. Leaven 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. — If. 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. Palece of the perfect flowers 

 larger than those of the sterile ones. — 71 . Through the summer. 

 Dry, shady soils. Common. 12 — 15 inches. 



Genus XL— ROTTBCEL'LIA. L. 

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



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

 flowers sterile and perfect. 



1. R. dimtdia'ta, (Mich.) {Stcnotaphrum Americanum, Schra.) 

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

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

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

 summer. On the sea-coast. 



Gents XIL— 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 palere, the lower one awned. Sta- 

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

 mucronate. Styles 2. 



1. 0. seta'iuus, (Roem.) (Panicum hirtcllum, 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. — If. Aug — 

 Oct. Rich, dry soils. 



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

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

 terminal pauicle ; 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. — 

 C- Aug. — Sept. Cultivated grounds. 2 — i feet. 



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

 length. 



