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. clavulif erum. 

 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. PI. ed. 2.^: 81. 1762. 

 - Panicum dissectum L. Sp. PI. 57. 1753. 



Paspalum membranaceum Walt. Fl. Carol. 75. 1788. 



A subaquatic glabrous creeping perennial with flat spreading blades about 

 5 cm. 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 cm. 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 cm. 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, 1.4 mm. wide, elliptic, acute, the thin faintly 

 3-nerved glume and sterile lemma pointed beyond the fr^iit; fruit elliptic- 



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