HITCHCOCK AND CHASE NORTH AMERICAN PANICUM. 



297 



Autumnal form branching from the middle and upper nodes, the branches erect or 

 ascending from the decumbent primary culm, the densely villous sheaths often over- 

 lapping on the shortened internodes, the blades more or less ovate-lanceolate and 

 strongly cordate-clasping, velvety pubescent, the panicles similar to the primary 

 ones but smaller. 



The autumnal form is not well developed in any of the specimens examined. Judg- 

 ing from the habit of the plant it appears to belong to the subgenus Dichanthelium 

 but more material is necessary to determine this with certainty. The characters of 

 the vernal form would place it in the group Lanuginosa, but the method of branching 

 is different from that of any of the species there segregated. The specimens often 

 resemble P. scoparium, and the species is therefore placed in this group, though 

 somewhat doubtfully because of the manifest ligules and the branching habit. 



DISTRIBUTION. 



Gravelly banks, fields and open forests, Mexico to Colombia; also in the Isle of 

 Pines. 



Mexico: Jalapa, Pringle 8089, C. L. Smith 1617; Zacualpan, Purpus 2160; a 



Mirador, Liebmann 323; San Cristobal, Bourgeau 3132 (Paris Herb.); Jical- 



tepec, Liebmann 324 (Paris Herb.); Orizaba, Botteri 705 (Gray Herb.); 



Schaffner 284 (Paris Herb.). 

 Guatemala: Sierra del Mico, Kellerman 6231, 6249. 

 Nicaragua: U. S. Pacific Expl. Exped. Wright. 

 Costa Rica: Aserri, Tonduz 1244; El General, Pittier 3358 (Instit. Costaric. 



Herb.). 

 Cuba: Isle of Pines, Palmer & Riley 1065. 

 Colombia: Near Jamundi, Pittier 940; Popayan, Lehmann 985 (Gray Herb.). 



180. Panicum aculeatum Hitchc. & Chase. 



Panicum aculeatum Hitchc. & Chase, Rhodora 8: 209. 1906. "Type Chase 2520 in 

 National Herbarium. In large clumps by small slough, border of woods, Takoma 

 Park, D. C, July 27, 1904; collected by Agnes Chase." The type is a vernal specimen 

 beginning to branch, with a mature primary panicle. 



DESCRIPTION. 



Vernal plants in large clumps; culms slender, 70 cm. to 1 meter high, ascending, 

 scabrous, harshly pubescent below; sheaths papillose-hispid with stiff, sharp-pointed 



hairs, a puberulent ring at the summit, the 

 uppermost usually glabrous; ligules minute, 

 membranaceous, ciliate; blades firm, stiffly 

 ascending or spreading, 12 to 20 cm. long, 9 

 ■ \ to 13 mm. wide, acuminate, involute-pointed, 

 scarcely narrowed to the rounded base, very 

 scabrous on the upper surface and toward 

 the apex beneath; panicles 8 to 12 cm. long, 

 about as wide, few-flowered, the slender, 

 flexuous, fascicled branches ascending or 

 spreading, naked at the base, scabrous, some- 

 times with a few viscid spots; spikelets 3 mm. 

 long, elliptic, minutely pubescent; first glume one-fourth to one-third as long as the 

 spikelet, acute; second glume and sterile lemma abruptly acute, slightly exceeding 

 the fruit; fruit elliptic, 2.7 mm. long, 1.3 mm. wide, minutely umbonate. 



Fig. 336. — P. aculeatum. From type specimen. 



a Panicum laxum Swartz was also distributed under this number. 



