HITCHCOCK AND CHASE TEOPICAL NORTH AMERICAN PANICUM. 475 



DISTEIBUTION. 



Wet places or in shallow water, margins of streams and ponds, mostly at low altitudes, 

 Cuba, Porto Rico, and Mexico to Trinidad and Paraguay. 



Colima: Alzada, Hitchcock 7067 . 

 Guatemala: Puerto Barrios, Siic^- 



coch 9147. 

 Cuba: Guanabacoa, Leon 919. 



Ariguanabo, Leon 1975, 1976. 



Habana,ie(5r!.4155. El Cano, 



Leon 1974. Laguna Jovero, 



Shafer 10912. Without local- 

 ity, Wright 3456 in part, 3861. 

 Porto Rico: Laguna del Tortu- 



guero, Chase 6804 . Lake Loisa, 



Chase 6778. Alto de Bandera, Chase 6471. Utuado, Britton & Cowell 432. 

 Leeward Islands: Guadeloupe, Dms 3178 (K. XJ. Herb.). 

 Trinidad: Pitch Lake, Eitchcoch 10099. 



Fig. 29. — Distribution of P. aquaticum. 



18. Panicum sucosum. sp. nov. 



DESCRIPTION. 



Plants perennial, glabrous throughout except as noted; culms few to several in a 

 tuft, 1 to 1.5 meters long, decumbent at base and rooting at the lower nodes, succulent; 

 sheaths rather loose, about as long as the internodes; ligule a densely ciliate membrane 

 about 1 mm. long; blades fiat or somewhat involute in drying, 15 to 30 cm. long, 

 3 to 9 mm. wide, linear, acuminate, scaberulous on both surfaces, sparsely pilose 

 above toward the base; panicle 15 to 30 cm. long, about 

 half as wide, the axis and branches somewhat scabrous, 

 the branches solitary or in pairs, rather stiffly spreading 

 or finally horizontal, as much as 15 cm. long, naked at 

 base for 1 or 2 cm., the internodes of the rachis mostly 3 

 to 5 cm. long, the branchlets appressed or ascending, 

 mostly from the lower side; spikelets short-pediceled, 

 somewhat appressed to the rachis, 3.3 to 3.7 mm. long, 

 about 1 mm. wide, lanceolate, acuminate, glabrous; first 

 glume one-fourth to nearly one-third the length of the 

 spikelet, broadly triangular, usually subacute, 3-nerved; 

 second glume and sterile lemma subequal, exceeding the 

 fruit and pointed beyond it, 7 to 9-nerved; fruit about 

 2.5 mm. long, 0.7 mm. wide, rather abruptly acuminate. 

 Type in the U. S. National Herbarium, no. 693325, col- 

 lected in water of a pond at Orozco, near Guadalajara, JaUsco, Mexico, September 29, 

 1910, by'A. S. Hitchcock (no. 7379). 



This species, which in the Revision ^ was included in P. elephantipes, differs from 

 P. dichotomiflorum in being perennial and in having larger spikelets; from P. aquati- 

 cum in its larger panicle and more pointed spikelets and fruit; from P. elephantipes 

 in having smaller, less succulent culms with narrower blades and in having less 

 acuminate fruit. 



Fig. 30.— p. sucosum. From 

 type specimen. 



1 Contr. U. S. Nat. Herb. 15: 54. 1910. 



