140 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Panicum rigens Salzm.; Steud. Syn. PI. Glum. 1:76. 1854, not Swartz, 1788. 

 This is given, as a synonym under P. rhigiophyllum Steud. Salzmann specimen.? from 

 Bahia, bearing this name have been examined in the herbaria at Munich and Halle 

 and in the United States National Herbarium. 



Panicum cayennense divaricatum Doell in Mart. Fl. Bras. 2^: 220. 1877. Based on 

 " Panicum scoparium Rudge * * * non Lam.. * * * nee Michaux." 



DESCRIPTION. 



Plants perennial, yellow-green or tawny; culms robust, 30 to 100 cm. high, erect or 

 somewhat geniculate at base, often zigzag, especially above, densely and harshly 

 villous; sheaths nearly equaling the internodes or overlapping, densely papillose- 

 villQUs or hirsute; ligules membranaceous, ciliate, about 1 mm. long, the hairs of the 

 ligule blending with the hairs of the upper surface of the blade: blades thick, linear, 

 15 to 40 cm. long, 5 to 10 mm. wide, rather rigidly ascending, flat or folded, slightly 

 narrowed toward the base, gradually long-acuminate, densely short-hirsute on both 

 surfaces or glabrate; panicles terminal and in the axils of the approximate upper 2 to 

 6 leaves, forming an oblong inflorescence one-third the height of the plant, or more, 

 each more or less included at base in the subtending sheath; branches pilose in the 

 axils, branching freely from the base, the branches and branchlets angled, scabrous, 

 the lower branchlets stiffly ascending, the upper and the long pedicels divaricate, 

 somewhat flexuous; spikelets about 3.5 mm. long, 1.5 mm. wide, turgid, somewhat 

 attenuate at base, strongly nerved, sparsely hirsute, the stiff hairs irregularly dis- 

 tributed; first glume about two-thirds the length of the spikelets, acuminate; second 

 glume and sterile lemma subequal, exceeding the fruit, abruptly pointed, the latter 

 subtending a palea and staminate flower; fruit 2.1 mm. long, 1.1 mm. wide, elliptic, 

 smooth and shining, a cartilaginous flap-like appendage at the base. 



All the cited specimens from Costa Rica have pubescent blades, while several of 

 those from South America have glabrate blades, e. g., Rusby & Squires 362, Spruce 93. 

 These specimens with glabrate blades, though apparently less common than those 

 with pubescent blades, are the typical form described by Meyer. 



DISTRIBUTION. 



Savannas, Costa Rica to Brazil. 



Costa Rica: Buenos Aires, Pittier 10576, Tonduz 3679, 4875; Los Palmares, Pit- 

 tier 10588; Helechales del General, Pittier 12064. 



Venezuela: Santa Catalina, Rusby & Squires 362. 



British Guiana: Jenman 5978. 



Dutch Guiana: Surinam, Hostmann 642. 



Brazil: Para, Spruce 93; Bahia, Salzmann; Organ Mountains, Wilkes Expl. 

 Exped. 9; without locality, Gardner 1178. 



Type U. S. National Herbarium no. 824039, collected in 1845, in the Province of 

 Minas Geraes, Brazil, by Widgren, "Ex herb. Brasil. Regnellian. Musei bot. Stock- 

 holm, " and distributed as "Panicum cayennense Lam." 



This species is related to P . rudgei with which and P . cayennense it has been confused . 



DISTRIBUTION. 



Brazil. The data on the labels of the specimens examined do not include habitat. 

 Brazil: Prov. Minas Geraes, Henschen & Regnall III 1367, Widgren in 1845; with- 

 out locality, Burchell A 101-2 (Gray Herb.), Riedel. 



