MANUAL OF THE GRASSES OF THE UNITED STATES 599 



136. PASPALUM L. 



Spikelets planoconvex, usualty obtuse, subsessile, solitary or in pairs, in 

 2 rows on one side of a narrow or dilated rachis, the back of the fertile lemma 

 toward it; first glume usually wanting; second glume and sterile lemma com- 

 monly about equal, the former rarely wanting; fertile lemma usually obtuse, 

 chartaceous-indurate, the margins inrolled. Perennials in the United States 

 (except P. boscianum and P. convexum), with one to many spikelike racemes, 

 solitary, paired, or several to many on a common axis. Type species, Paspalum 

 dissectum. Name from Greek paspalos, a kind of millet. 



Several species inhabiting meadows and savannas furnish considerable 

 forage. Paspalum dilatatum is valuable for pasture, especially for dairy cattle 

 in the Southern States, where it has been cultivated under the name water 

 grass and recently Dallis grass. In the Hawaiian Islands, Australia, and some 

 other countries, where it is called paspalum or paspalum grass, it is valuable 

 as a pasture grass. P. puhiflorum var. glabrum is rather abundant in some 

 regions and is considered a good forage grass. Vasey grass, P. urvillei, is used to 

 a limited extent for hay and, when young, for pasture; the panicles, after the 

 spikelets have fallen, also make excellent whisk brooms for brushing lint. 

 In the Southern States (Virginia to Florida and even to California) P. distich- 

 um, because of its extensively creeping stolons, is useful for holding banks of 

 streams and ditches. 



la. Rachis foliaceous, broad and winged. 

 Racemes falling from the axis, rachis extending beyond the uppermost spikelet. 



3. P. FLUITANS. 



Racemes persistent on the axis; rachis with a spikelet at the apex. 



Spikelets 2 mm. long, obovate-oval 1. P. dissectum. 



Spikelets more than 3 mm. long, pointed 2. P. acuminatum. 



lb. Rachis not foliaceous nor winged (slightly winged in P. boscianum). 

 2a. Racemes 2, conjugate or nearly so at the summit of the culm, rarely a third below. 

 Spikelets elliptic to narrowly ovate. 



Plants with creeping rhizomes or stolons. 



Second glume and sterile lemma glabrous; spikelets flattened 4. P. vaginatum. 



Second glume pubescent; spikelets relatively turgid 5. P. distichum. 



Plants in dense tufts, without creeping rhizomes 11. P. almum. 



Spikelets suborbicular, broadly ovate or obovate. 



Spikelets concavo-convex, sparsely long-silky around the margin; plant stoloniferous. 



31. P. conjugatum. 

 Spikelets plano-convex, not silky-margined; plants not stoloniferous. 



Spikelets 3 to 3.5 mm. long 9. P. notatum. 



Spikelets 2 to 2.5 mm. long 10. P. minus. 



2b. Racemes 1 to many, racemose on the axis, not conjugate. 



3a. First glume developed on at least one of the pair of spikelets (often obsolete in some 

 pairs in Nos. 22 and 23). 



Spikelets turgidly biconvex 48. P. bifidum. 



Spikelets plano-convex. 



Plants without rhizomes; culms tufted; spikelets pubescent 24. P. langei. 



Plants with stout scaly rhizomes; culms mostly solitary; spikelets glabrous. 



Blades flat, 8 to 15 mm. wide 22. P. unispicatum. 



Blades folded at base, terete above, not more than 2 mm. wide. 



23. P. monostachyum. 

 3b. First glume normally wanting (occasionally developed on 1 to few spikelets in a 

 raceme). 

 4a. Racemes terminal and axillary, the axillary sometimes hidden in the sheaths and 

 perfecting grains cleistogamously, terminal inflorescence of 1 to 3, rarely to 6 

 racemes (see also P. unispicatum and P. monostachyum). 

 5a. Spikelets not more than 1.8 mm. long (or sometimes 1.9 in P. dehile and P. 

 propinquwn), usually 1.5 to 1.7 mm. (see also exceptional P. ciliatifolium). 

 Blades conspicuously ciliate, otherwise nearly glabrous. 



