20 POACEAE. 



10. Paspalum distichum L. Pugil. PI. Jam. 5. 1759. 



Culms 1-6 dm. tall, from a long stout rootstock; sheaths compressed, 

 keeled, usually crowded and overlapping, especially at the base and on the 

 innovations, glabrous, or more or less hairy on the margins; leaves commonly 

 less than 1 dm. long, 3-6 mm. wide, usually glabrous; racemes terminal, in 

 pairs, ascending, 2-5 cm. long; spikelets singly disposed, ovate, 2.5-3 mm. 

 long, acute, the 2 oufer scales firm, 5-nerved, rarely 7-nerved, the first scale 

 glabrous, the second appressed-pubescent, the third apiculate, pubescent at 

 the apex. 



Fresh water marsh, New Providence : Bermuda ; Virginia to Florida, Texas 

 and California, and north on the coast to Oregon ; the West Indies and tropical 

 America. Hitchcock's plant from Fortune Island, referred to this species, proves 

 to be P. vaginatiim Sw. JOINT-GRASS. 



11. Paspalum vaginatum Sw. Prodr. 21. 1788. 



Culms 2-6 dm. tall, from a long stout rootstock ; sheaths compressed, 

 keeled, usually crowded and overlapping, at least at the base and on the inno- 

 vations, glabrous; leaves folded, or involute when dry, 1.5 dm. long or less, 

 2-4 mm. wide, glabrous, or sparingly hairy; racemes terminal, usually in 

 pairs, rarely more >or but a single one, erect or ascending, 3-7 cm. long; spike- 

 lets singly disposed, ovate-lanceolate, acute, 3-4 mm. long, the 2 outer scales 

 glabrous, thin, the first scale 4-nerved, the lateral nerves approximate at the 

 margin, the midnerve suppressed, the second scale 5-nerved, the lateral nerves 

 rather near together, the third scale glabrous at the apex or with 2 or 3 hairs. 



Borders .of marshes, New Providence, Watling's Island, Fortune Island, and 

 Inagua : Bermuda ; southern United States ; West Indies ; tropical continental 

 America. SHEATHED PASPALUM. 



Paspalum sp. Hitchcock and Chase (Contr. U. S. Nat. Herb. 18: 316) record 

 a plant of this genus from Inagua, not certainly referable to any known species. 



11. PANICUM L, Sp. PI. 55. 1753. 



Annuals or perennials, various in habit, with open or contracted panicles. 

 Spikelets 1-2-flowered, when 2-flowered the lower one staminate only. Scales 

 4, the 3 lower membranous, empty, or the third with a staminate flower, vary- 

 ing in the same species; the inner or fourth scale chartaceous, shining, enclos- 

 ing a palet of similar texture and a perfect flower. Awns none. Stamens 3. 

 Styles distinct. Stigmas plumose. Grain free, enclosed in the hardened fruit- 

 ing scale and palet. [Old Latin name for some grass, probably the cultivated 

 sorghum, referring to its panicle, taken from Pliny.] About 500 species, in 

 temperate and tropical regions. Type species: Panicum miliaceum L. 



A. Palet little or not at all enlarged when mature. 



1. Inflorescence consisting of spike-like often 1-sided branches or racemes. 



Spikelets singly disposed, in 2 distinct rows, on very short equal pedicels ; 



first scale truncate. 1. P. yeminatum. 



Spikelets otherwise arranged, on unequal pedicels ; 



first scale acute or obtuse, never truncate. 

 Fourth scale of the spikelet transversely rugose. 

 Panicle branches terminating with a spikelet, 



no prolongation. 

 Pedicels shorter than the spikelets. 



Stems all fertile, the nodes naked, or 



occasionally sparsely pubescent. 

 Outer scales of the spikelet with no 

 cross-veinlets ; stems often rooting 

 at the lower nodes. 2. P. adspersum. 



Outer scales of the spikelet with 

 manifest cross-veinlets ; stems rare- 

 ly rooting at the lower nodes. 3. P. fasciculatum. 



