414 Karl M. Wiegand and Arthur J. Eames 



[A. PSILOSTACHYA DC. 



In sod, L. V. R. R. yards near Barge Canal Terminal, 1925 {W. C. Muenscher), 

 doubtfully established. Native of w. U. S.] 



15. Xanthium (Tourn.) L. 37 3S 

 1. X. orientale L. Cockle-bur. Clotbur. 



Damp sandy or gravelly banks and shores ; frequent. Aug.-Sept. 



Widely distributed in N. A. except in the colder parts of Canada. Found also in 

 Eu. and Cent. Am., and perhaps in other countries. 



The following forms are found in the Cayuga Lake Basin: (1) Burs glabrous 

 or minutely puberulent and atomiferous, fusiform, averaging somewhat smaller than 

 in the other forms (X. chinense Mill., X. pungens Wallr., X. glabratum Britton, X. 

 americanum Britton & Br., possibly Walt., X. canadcnse of Gray's Man., ed. 7, and of 

 Cayuga Fl. (2) B'urs more or less hispid, the body ellipsoidal with generally 

 prominent beaks (X. italicum Mor., X. pcnnsylvanicum Wallr., X. commune Britton 

 and of Gray's Man., ed. 7, X. canadense, var. echinatum, in part, of Cayuga Fl.). 

 (3) Burs hispid, the body ovoid, broadly elliptic-ovoid, or oval, the beaks less 

 prominent (X. glanduliferum Greene?, X. canadense, var. echinatum, in part, of 

 Cayuga Fl., X. echinatum, in part, of Gray's Man., ed. 7). (4) Spines far apart and 

 few in number, otherwise generally as in no. 2 (X. Wootoni Cockll.). The spines 

 in this last-named form vary in number toward the normal, and the plants occur as 

 individuals in otherwise normal colonies. In each of the above-named forms the 

 spines vary greatly in shape and abundance. 



16. Heliopsis Pers. 

 1. H. helianthoides (L.) Sweet. (H. laevis of Cayuga Fl.) 



Stream banks and open thickets, on alluvial bottom lands ; common, and gener- 

 ally distributed. June 20-Aug. 



N. Y. to Ont. and N. Dak., southw. to Fla., Tenn., and 111. ; rare or absent on the 

 Coastal Plain. A plant of the rich soils of the Mississippi Valley. 



Variable in the roughness of the foliage. 



17. Rudbeckia L. 



a. Disk dark purple or brown ; stem rough-hairy, 1 m. high or less. 



b. Leaves, or some of them, 3-lobed or 3-divided; chaff awned, smooth; pappus a 



minute crown. 1. R. triloba 



b. Leaves, or some of them, coarsely toothed or incised; chaff acute, slightly ciliate 

 or erose ; pappus a short crown. 2. R. speciosa 



31 Several years ago I undertook a revision of the American Xanthiums, making use of the 

 material in the Gray Herbarium. After a prolonged but unsuccessful effort to prepare a satis- 

 factory treatment, the problem was laid aside. I am now greatly in doubt as to the existence of 

 more than one real species in the group represented by X. chinense Mill., X. pennsylvanicum 

 Wallr., X. italicum Mor., and other related forms. The foliage in these forms is practically 

 identical, and the only differences of any moment are in the burs, which are indeed highly 

 variable. Extreme forms of burs, however, are often found in the same colony, as though 

 sporadically produced. A large suite of specimens is almost sure to show a nearly or quite 

 unbroken series through the various forms. In every attempt to segregate the burs into species, 

 so many transitional specimens have been found as to do unwarranted violence to any species 

 concept. It is probably wise to treat all North American Xanthiums as one species except X. 

 spinosum L. and possibly X. strumarium L. and X. echinatum Murr. X. strumarium, however, 

 is scarcely distinct, and with more study may also be included. X. echinatum may be a real 

 species, as it has a distinct coastal range and seems to behave as though genetically distinct. 

 Provisionally the oldest name, X. orientale L., is here taken for the group (when X. strumarium 

 and X. echinatum are excluded). It has not seemed wise to assign varietal names within the 

 species at present. — K. M. Wiegand. 



aa See revision by Millspaugh and Sherff, Field Mus. Nat. Hist. Pub. Bot. 4, no. 2. 1919. 



