HITCHCOCK — REVISIONS OF NORTH AMERICAN GRASSES. 201 



Panicum triquetrum Willd.; Doell. in Mart. Fl. Bras. 2 2 : 161. 1877, as synonym 

 of Panicum caudatum Lam. The type is no. 18809 in the Willdenow Herbarium, sent 

 by Vahl from "America" (probably Brazil). 



Chaetochloa rariflora Hitchc. & Chase, Contr. U. S. Nat. Herb. 18: 349. 1917. 

 Based on Setaria rariflora Mikan. 



DESCRIPTION. 



Plants perennial, tufted; culms erect, or decumbent at base, glabrous, mostly 30 

 to 60 cm. tall; sheaths pubescent with short ascending hairs or glabrate, keeled, 

 mostly overlapping; ligule densely ciliate, less than 1 mm. long; blades elongate 

 and narrow, pubescent on both surfaces, narrowed at base, usually 2 to 3 mm. wide, 

 rarely over 5 mm.; panicles narrow, tapering above, 10 to 15 cm. long, often less, the 

 axis loosely villous, the hairs 

 mostly less than 1 mm. long; 

 branches ascending, the lower 5 

 to 10 mm. long, or often shorter, 

 rarely longer, the panicle then 

 being loosely or interruptedly 

 spikelike; bristles usually one 

 below each spikelet, flexuous, 

 antrorsely scabrous, 4 to 7 mm. 

 long, or often scarcely exceeding 

 the spikelets; spikelets about 2 

 mm. long, turgid on the convex 

 side; first glume a little less than 

 half the length of the spikelet, 

 3-nerved ; second glume about two- 

 thirds as long as the spikelet, 7- 

 nerved ; sterile lemma as long as 

 the fertile, 5 to 7-nerved, the palea 

 well developed; fertile lemma 

 acutish, finely and sharply cross- 

 ridged. 



This species differs from G. setosa 

 chiefly in the long narrow blades 

 and the usually narrower and less 

 bristly panicle. The second 

 glume is shorter and usually 7- 

 nerved. The two forms are given 

 specific rank because the speci- 

 mens from Brazil agree in having slender, rather lax blades and narrow, few-flowered, 

 interruptedly spikelike panicles like the type of C. rariflora. Chaetochloa setosa is con- 

 fined to the West Indies and adjacent parts of South America. There are no specimens 

 known from Brazil. In Trinidad it is found only on the outlying islet Chacachacare. 

 Because of the slightly different aspect and the different geographical range it seems 

 better to recognize the two forms as species rather than varieties, though they are 

 closely related. 



DISTRIBUTION. 



Dry hills, Porto Rico to Brazil. 

 Alabama: On ballast, Mobile, Mohr in 1892. 



Porto Rico: "Under cactus on cliff facing sea," Boqueron, Chase 6502. 

 Virgin Islands: St. Croix, Ricksecker 67. 

 Leeward Islands: Antigua, Wullschlaegel 629. 



Brazil: Bahia, Dorsett & Popenoe 433b. Rio de Janeiro, Langsdorff; Widgren in 1844; 

 Wilkes Expl. Exped.; Rose 20188, 20214. Without locality, Burchell 1251; Glaziou 

 16574; Gardner 139; Riedel. 



Fig. 58. — Cliaetochloa rariflora. From Ricksecker 67 , St. Croix. 



