306 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Spikelets 1.5 to 1.8 mm. long, elliptic. 
Primary pedicel much shorter than its spikelet, 
the spikelets crowded. 
Racemes 2 to 3 cm. long, rather thick. 
32. P. caespitosum. 
Racemes 5 to 10 cm. long, slender. 
35. P. glabrum. 
Primary pedicel nearly as long as its spikelet, the 
spikelets not crowded; racemes slender. 
33. P. portoricense. 
Racemes solitary. 
Blades not over 1 mm. wide, concavo-convex or sub- 
terete in cross section. 
Plants delicate; blades subterete. 
30. P. capillifolium. 
Plants wiry; blades concavo-convex, 
21. P. leptocaulon. 
Blades or some of them 2 mm. or more wide, flat or 
involute. 
Nodes glabrous; culms leafy; blades flat; spikelets 
in pairs. 
Blades 5 to 8 mm, wide______ 38. P. propinquum. 
Blades not over 3 mm. wide. 
47. P. clavuliferum. 
Nodes appressed-pubescent; culms delicate, the 
leaves mostly clustered at the base; spikelets 
solitary (rarely a few paired). 
Spikelets pubescent__-....-______ 29. P. poiretii. 
Spikelets glabrous. 
Spikelets 1 mm. long___-______ 27. P. rupestre. 
Spikelets 1.5 mm. long________ 28. P. leoninum. 
1. Paspalum dissectum (L,) L. Sp. Pl. ed. 2. 1: 81. 1762. 
Panicum dissectum Li, Sp. Pl. 57. 1758. 
Paspalum membranaceum Walt. Fl. Carol. 75. 1788. 
A subaquatic glabrous creeping perennial with flat spreading blades about 
5 gm. long and few short racemes, the rachis broad, membranaceous, inflexed 
over the base of the small pale oval spikelets. 
On muddy banks of ponds and ditches or in shallow water, southeastern 
United States and Cuba. Originally described from North America, probably 
Delaware; P. membranaceum described from South Carolina. 
2. Paspalum serratum sp, nov. 
A glabrous aquatic perennial with rather soft elongate sparingly branching 
culms, aS much as 1.5 meters long, bearing a few rootlets at the nodes, the 
internodes flattened, more or less angled in drying; sheaths thin, loose, over- 
lapping on the flowering branches; ligule 2 mm. long, hyaline, erose; blades 
suberect, soft, thin, flat, 3.5 to 9 em, long, 4 to 7 mm. wide, abruptly rounded 
at base; panicles terminal on leafy branches, short-exserted or included at base, 
consisting of 2 (rarely 1) divergent racemes, the slender common axis about 
12 mm. long; racemes 3 to 4.5 em. long, the rachis membranaceous, green, 3 
to 3.5 mm. wide, the margins inflexed over the base of the spikelets, naked at 
the base, terminating at the base of the uppermost spikelet; spikelets solitary 
in two rows, 3.2 to 3.4 mm. long, 14 mm. wide, elliptic, acute, the thin faintly 
8-nerved glume and sterile lemma pointed beyond the fruit; fruit elliptic. 
