HITCHCOCK — REVISIONS OF NORTH AMERICAN GRASSES. 177 



Chaetochloa impressa Hitchc. & Chase, Contr. U. S. Nat. .Herb. 18: 350. 1917. 

 Based on Panicum impressum Nees. 



Setaiia sphaerocarpa Hubbard, Contr. Gray Herb. n. ser. 52: 60. 1917. Based on 

 Panicum sphaerocarpum Salzm. 



Tbis was described by Grisebach : as Setaria onurus and by Hitchcock and Chase 2 

 as Chaetochloa onurus, but a reconsideration of the type leads to the conclusion that 

 the original Panicum onurus Willd. from Montevideo (as described by Trinius) 3 is a 

 different species, later described as Setaria caespitosa Hack. & Arech. 4 Panicum 

 onwius was earlier mentioned as a synonym by Nees (see note under Chaetochloa 

 macrostachya) . The first valid publication of the name, however, was by Trinius 

 (loc. cit.), his type collected at Montevideo by Sello. 



DESCRIPTION. 



Plants perennial; culms glabrous, scabrous below the panicle, 1 to 1.5 meters tall, 

 often geniculate at base; sheaths glabrous or usually scabrous toward the summit, 

 villous on the margin, densely hispid on 

 the collar; ligule densely pilose, 2 to 3 

 mm. long; blades flat, more or less scab- 

 rous, narrowed at base, acuminate at 

 apex, as much as 35 cm. long and 2 cm. 

 wide; panicles rather densely flowered, 

 narrowed toward summit but not atten- 

 uate, somewhat interrupted or lobed be- 

 low, 15 to 30 cm. long, 2 to 3 cm. wide, 

 the branches ascending, the lower about 

 2 cm. long, the axis villous with hairs 1 

 to 2 mm. long; bristles 1 or 2 below each 

 spikelet, 1 to 2 cm. long, flexuous, re- 

 trorsely scabrous and often also an- 

 trorsely toward the base, sometimesbarb- 

 lets directed both ways intermixed, pale 

 or tawny, becoming implicate and some- 

 what one-sided with age; spikelets sub- 

 spheric, about 2 mm. long, very turgid 

 on one side and somewhat convex on the 

 other; first glume about 1 mm. long or 

 a little less, 5-nerved; second glume 

 about two-thirds as long as the spikelet 

 but at maturity pushed aside, exposing 

 nearly half the fertile lemma, 7 to 

 9-nerved; sterile lemma as long as the 

 fertile, 5 to 7-nerved, the nerves less 



distinct than those of the glumes, the palea well developed; fertile lemma very 

 turgid, yellowish brown at maturity, rather indistinctly cross-wrinkled, the palea 

 convex. 



This species resembles C. vulpiseia, but is less robust and has retrorsely scabrous 

 bristles and subspheric spikelets. 



Hitchcock's no. 9926, from Puerto Colombia, has pubescent sheaths and blades. 



1 Fl. Brit. W. Ind. 555. 1864. 



2 Contr. U. S. Nat. Herb. 18: 349. 1917. 



3 Mem. Acad. St. Petersb. VI. Sci. Nat. 1 : 226. 1834. See also Nees, Agrost- 

 Bras. 251. 1829. 



4 Anal. Mus. Nac. Montevideo 1 : 166. 1894. 



Fia. 42. — Chaetochloa tenax. From Tracy 9090, Cuba. 



