782 ORDER 156. GRAMINEJB. 



3 P. setaceum MX. Culm ascending from a decumbent base, very slender, 1 to 

 2f, with very remote joints; Ivs. lance-linear, 3 7' by 2 3", ciliate and soft 

 hairy; sheaths pubescent, upper one very long; spike generally solitary, often 2, 

 on a long, very slender peduncle, sometimes with another scarcely exserted from 

 the sheaths; spikelets plano-convex, with the flat side out, |" diam., 1 or 2 on 

 each very short pedicel, appearing 2 3-rowed in the 1-sided spike. Dry fields, 

 Mass., to 111. and S. States. Aug. (P. debile and ciliatifolium MX.) 



/3. LONGIPEDUNCULATUM. Larger, less hairy, and spikelets evidently 3-rowed. 

 S. States. (P. longip. LeC.) 



4 P. lasve MX. Culm erect, rather firm, 18' 3f, glabrous ; Ivs. generally smooth, 

 pilous only at the base, broadly linear; lower sheaths sometimes hairy, spikes 

 2 6, alternate, spreading, with a few long, white hairs at the base ; spikelets in 2 

 rows ; rachis flexuous, flat on the back ; pedicels undivided, with one spikelet ; 

 spikelets twice as large (!'' diam.) as in the preceding ; glume orbicular-ovate, 

 3-veined. Grassy banks of rivers, Conn, to Tnd. and S. States. Aug. Quite vari- 

 able, including several reputed species. 



j3. UNDULOSUM. Lvs. rather long and broad, with wavy-margins. (P. Lecon- 



tianum Schult.) 

 y. FLORIDANUM. Spikelets enlarged (near 2'' long), glume 5-veined. (P. ma- 



crospermum Flgg.) 

 6. ALTISSIMUM. Strict and tall ; sheaths much compressed. (P, altissimum LeC.) 



5 P. angustifdlium Le Conte. Culm erect, wiry, glabrous, 2f high ; Ivs. glab- 

 rous, narrowly linear, almost setaceous, compressed carinate, 9 to 18' long ; sheaths 

 long, smooth; spikes 2 or 3, alternate, divaricate, I to 2' long, with a few hairs at 

 base; spikelets orbicular, 1" diam. in 2 rows, with a very narrow rachis. 1 Wet 

 places, G-a., Fla. to La. A distinct species. Seeds blackish. 



6 P. dasyphyllum Ell. Culm decumbent at base, 12 to 30' high, glabrous: 

 . Ivs. broadly linear, clothed with copious soft hairs as well as the long sheaths ; 



spikes 2 to 4, large, spreading, the ped. slightly exserted from the upper sheath ; 

 spikelets oval, obtuse, large, in 3 rows ; teeth of the rachis 2-flowered. Dry fields. 

 S. States, common. ,>? Jl. Oct. 



7 P. latifolium Le Conte. Glabrous; culm erect, stout, tall (2 to 3f), from a 

 slightly decumbent base; Ivs.Jlat, large, lance-linear, G to 12' by 5 to 10", margins 

 ciliate ; sheaths hairy at throat, shorter than the long internodes ; spikes 2 to 4, 



2 to 4' long, alternate, suberect, pilous at base; spikelets lapge (1|" diam.), in. 



3 rows on the narrow, flexuous racbis. 1[. Car. to Fla. and La. 



8 P. tentie Kunth. Glabrous ; culm erect, very slender h>s. narrow, very long, 

 ciliate on the margins, sheath ciliate ; spikes 4 or 5, very slender, alternate, 

 spreading, hairy at base ; spikelets orbicular, in 3 rows ; rachis flexuous, narrow, 

 the teeth 2-flowered. H N. J. to Ga. (Le Conte). Differs from No. 5, in its ciliate 

 Ivs. and 3 -nerved spikelets. 



9 P. arundinaceum Poir. "Glabrous; Ivs. somewhat sword-shaped (com- 

 pressed-car inate}, the margin scabrous ; spikes alternate, elongated ; spikelets in 

 3 rows ; gls. (gl. and pale) equal, obtuse. Carolina." Poiret. 



10 P. preecox Walt. Glabrous throughout ; culm erect ; Ivs. lance-linear, very 

 long ; spikes 3 to 5, alternate, dense-flowered, with a tuft of long hair at base ; 

 rachis linear, straight (not flexuous), narrower than the 3 rows of very smooth, 

 orbicular, compressed spikelets; gls. 3-veined. 1 Wet places. Car. to Fla. May. 

 Aug. (P. lentiferum Lam.) 



11 P. fluitans Kunth. Culm decumbent and ascending 10 to 20', generally 

 floating; Ivs. scabrous, lance-linear, 2 to 5' by 4 to 6"; sheaths inflated, open, 

 ciliate at base ; spikes 20 to 50, 1 to 2-|' long, the lower somewhat verticillate ; 

 rachis foliaceous, nearly 1" broad, covering the 2 rows of ovate, acute spikelets 

 and projecting in a point beyond them. (1) River swamps, S. Ill to Va. and S. 

 States. Oct. (P. mueronatum Muhl. Ceresia, Ell.) 



! 12 P. Walterianum Schult. Culm decumbent, branching, ascending ; Ivs. 

 glabrous, lance-linear, 2 to 4' by 3 to 5" ; sheaths open, all glabrous; spikes 2 or 

 3 on each branch, 1 to 2' long ; rathis very broad (near 2"), covering the 2 rows 

 of oval, acute spikes but not projecting beyond them. (J)Wet soils, Car. to Fla. 

 . and La. JL Sept. (P. vaginatum Ell.) 



