ORDER 156. GRAMINE^E. 781 



subequal, and about equaling the oblong, terete, deciduous, short-stiped 

 flower; lower pale coriaceous, involute, inclosing the caryopsis and tipped 

 with a simple, jointed awn; scales linear-oblong. 2 Fls. in a slender 

 or spike-like panicle. 



Sheaths all leaf-bearing. Stipe of the flower nearly glabrous, very short No. 1 



Sheaths, at least the upper, leafless. Stipe conspicuously bearded Nos. 2. 8 



1 O. melanocarpa MuhL Culm erect, simple, leafy, 18 24'; panicle simple, 

 flexuous, few-flowered ; spikelets racemous, ovoid-lanceolate ; glumes acuminate, 

 mucronate, 5 6" in length, smooth; pales hairy, nearly black when ripe, the 

 lower one tipped with an awn an inch in length ; fruit black. Rocky hills, U. S. 

 and Can., frequent Aug. (Piptatheram nigrum Torr.) 



2 O. asperifolia MX. Culm nearly naked, purple at base, 10 20'; Ivs. subrad- 

 ical, erect, rigid, pungent at the point, nearly as long as the stem, cauline ones few 

 and very short ; spikelets in a racemous, simple, flexuous panicle, 2 tQ 4' long, 

 1 2 upon each branch; glumes abruptly acuminate; pales white, the lower one. 

 with a long, bent awn. Woods, N. States N. to Subarctic Am. Leaves green 

 through the winter. Caryopsis white, about as large as rice, farinaceous. May. 

 (Urachne Trin.) 



3 O. Canadensis Torr. Culms slender, 9 to 18' high, naked above; lower 

 sheaths bearing rigid, involute-filiform Ivs. ; pan, 1 to 2' long, narrow, the branches 

 mostly in pairs ; gls. often purplish, 1 to 2" long ; pales white, bearded with whit- 

 ish hairs, the awn short and deciduous or wanting. Rocky woods, N. Eng., to the 

 shores of L. Superior. May. (Stipa juncea MX., nee L. S. Canadensis Poir. 

 Urachnc Trin. Milium pungens Torr.) 



15. PAS'PALUM L. (Gr. naa7ra^.o^ millet; from the resemblance 

 of the seeds.) Spikelets plano-convex, in unilateral spikes; glumes 

 (apparently) 2, membranous, equal, ovate or orbicular, closely pressed 

 to the fertile flower ; stigmas plumous, colored ; caryopsis coated with 

 the smooth, coriaceous pales, (But theoretically, the lower glume is 

 obsolete and its place supplied by the empty pale of an abortive flower. 

 In Nos. 19 and 20 the lower glume appears, under a lens, as a mere 

 rudiment) Spikes linear, the fls. in 2 or 4 rows; rachis not jointed ; 

 pedicels articulated, 



PASPALUM. Spfkelets suborbicular, obtuse, crowded. Spikes alternate. (*) 



* Spikes many <7 to 80), with the spikelets mostly 4-rowed ; Nos. 1, 2 



* Spikes few (1 to 3), mostly solitary, slender <l v wide), 2 or 3-rowed. No. 3 



* Spikes few (2 to 6) with the spikelets in 2 rows, near 2" wide Nos. 4, 5 



with the spikelets in 3 rows, near 3" broad, (a) 



a Leaves very hairy. Culms decumbent. No. 6 



a Leaves only ciliate on the margins Nos. 7, S 



a Leaves very glabrous, margins scabrous Nos. 9, 10 



DIGITARIA. Spikelets ovate or lanceolate, acute. Spikes mostly digitate. (**) 



** Rachis leaf-like, broader than the 2 rows of spikelets beneath it Nos. 11, 1-2 



** llachis narrow, triquetrous or flat, with the spikelets close-appsessed. (b) 

 b Glumes (glume and pale) about equal, as long as the flower, (c) 



C Spikelets lanceolate. Spikes in pairs or threes Nos. 13, 14 



C Spikeiets ovate. Spikes 2 to 4 ofteaer Is pairs. Nos. 1517 



b Glume scarce half as long as the pale. Spikes 5 to 12, clustered Nos. IS, 19' 



** Eachis filiform with the spikelctfs loose and subremote. Nos. 20, 2 1 



1 P. virgatum L. Culms decumbent .at base, glabrous, 18 to 30'; Ivs. broad- 

 linear, rough-edged, 12 to 18' by 5 to 6''- sheaths glabrous, with a hairy throat; 

 spikes numerous (7 to 12); rachis straight (jiot flexuous), flat, narrower than the 

 4-rowed, dense, orbicular, obtuse spikelets. H Moist soils, S. States, common in 

 the low country. Jl. Oct. A very smooth variety is the P. confertum Le Conte. 



/?. PDSPURASCEXS. Culm below, Ivs. and sheaths dark purpk-. (P. purpu- 

 rascens Ell.) 



2 P. undulatum Poir. ''Plant very glabrous; Ivs. long and linear, someiritat 

 carinate- margin scabrous, base ciliate, sheaths glabrous; spikes many; rach!s 

 fiat, glabrous, margins scabrous, narrower than the 2 to -rowed spikelets ; lower 

 glume pubescent, upper glume (palea) smooth, transversely plaited near the margins.)" 

 Kunth. Ga. and Fla. A variety of No. 6 ? (P. plicatum MX.) 



