HITCHCOCK AND CHASE NOKTH AMERICAN PANICUM. 191 



viride Vasey" in Vasey's handwriting. Of these a vernal specimen collected by 

 L. F. Ward, Woodley Park, Washington, D. C, 1881, is chosen as the type, since it is 

 entirely without pubescence, while the other specimens marked "var. viride" by 

 Vasey have pubescent spikelets or nodes, or are fragmentary. 



Panicum dichotomum divarication Vasey, U. S. Dept. Agr. Div. Bot. Bull. 8: 30. 

 1889. No specimen nor locality is cited. There are in the National Herbarium two 

 specimens of the autumnal form of P. dichotomum marked "var. divaricatum " 

 by Vasey. Of these, S. M. Tracy 127, Lake, Mississippi, is chosen as the type, since 

 the other specimen is nearly devoid of spikelets. Certain other specimens marked 

 by Vasey do not correspond to the description. 



Panicum nitidum pauciflorum Britton, Trans. N. Y. Acad. 9: 14. 1889. Based on 

 "P. dichotomum var. pauciflorum Vasey in Columbia College Herbarium." The 

 type is labeled "Panicum, Shady moist grounds, July" and consists of several spar- 

 ingly branched culms of P. dichotomum with small panicles. Vasey's herbarium name 

 had not been published. 



Panicum nitidum viride Britton, Trans. N. Y. Acad. 9 : 14. 1889. % Based on P. dicho- 

 tomum viride Vasey. 



Panicum dichotomum commune Wats. & Coulter in A. Gray, Man. ed. 6. 633. 1890. 

 No specimen nor locality is cited. The name as published is "(a) commune''' and was 

 probably meant to designate the common vernal form. No specimen marked "var. 

 commune" could be found in the Gray Herbarium. 



Panicum ramulosum viride Porter, Bull. Torrey Club 20 : 194. 1893. Presumably 

 based on P. dichotomum viride Vasey, since "(Vasey)" is given after the varietal name. 



DESCRIPTION. 



Vernal form often purplish; culms 30 to 50 cm. high, erect, from a knotted crown, 

 the nodes naked or the lower with a few spreading hairs; sheaths less than half the 

 length of the internodes, sometimes ciliate on the margin, otherwise glabrous, or the 

 lowermost rarely sparingly pubescent; blades spreading, 5 to 11 cm. long, 4 to 8 mm. 

 wide, acuminate, slightly narrowed toward the base, glabrous on both surfaces, some- 

 times with a few long hairs on the margin at the base, the basal blades lanceolate- 

 ovate, long-ciliate on the margin near the base; pani- 

 cles long-exserted, 4 to 9 cm. long, the axis and spread- 

 ing branches nexuous, spikelet-bearing toward the 

 ends; spikelets 2 mm. long, 0.9 mm. wide, elliptic, 

 glabrous or rarely pubescent; first glume one-third 

 the length of the spikelet, subacute; second glume 

 and sterile lemma rather faintly nerved, the glume 

 shorter than the fruit at maturity; fruit 1.8 mm. 

 long, 0.9 mm. wide, elliptic. 



Autumnal culms muchi branched at the middle 

 nodes, the lower portion usually erect and devoid of 

 blades, thus giving the plants the appearance of diminutive trees as described by 

 Gronovius and Linnaeus; blades much reduced and very numerous, often involute. 



This common and widely distributed species can be distinguished by its lack of 

 pubescence, its smooth spikelets, 2 mm. long, and its erect autumnal form. 



A few specimens, such as Hitchcock 1292, Pollard 323, and Ward in 1881, from Wash- 

 ington, D. C, which show all the other characters of P. dichotomum have pubescent 

 spikelets. 



Fig. 191.— P. dichotomum. From type 

 specimen in Gronovius Herbarium. 



