962 Compositae Xanthium 



9148. XANTHIUM [Tourn.] L. Cocklebur 



[Millspaugh & Sherff. Revision of the North American species of 

 Xanthium. Field Museum Botanical Series 4: 9-51. 14 pi. 1919. Mills- 

 paugh & Sherff. Xanthium. North American Flora 33: 37-44. 1922. 

 Widder: Die Arten der Gattung Xanthium. Fedde Repertorium 20: 1-221. 

 Tafel 4, Karte 4. 1923. Wiegand & Eames. Xanthium. 1 Flora of the 

 Cayuga Lake Basin: 414. 1926. Symons. Studies in the genus Xanthium. 

 Bot. Gaz. 81 : 121-147. 3 pi. 1926.] 



Leaves attenuate at both ends, mostly less than 2 cm wide, with a strong, 3-pronged 



prickle at the base of each 1. X. spinosum. 



Leaves cordate or ovate, more than 3 cm wide, without prickles at the base. 



Body of fruit and prickles glabrous or nearly so 2. X. pennsylvanicum. 



Body of fruit and prickles more or less hispid 3. X. italicum. 



1. Xanthium spinosum L. Spiny Cocklebur. Map 2107. This species 

 has been reported from Clark, Franklin, Jefferson, and Putnam Counties. 

 Young, in 1875, said that it was spreading and not uncommon ten years 

 before in Jefferson County, mostly along roadsides. I have traveled all of 

 the principal roads of Jefferson County and have done considerable 

 botanical work there and I have never seen it. This would indicate that 

 for some reason it is not spreading. It may be that landowners have 

 recognized the plant as a weed and eradicated it. 



I found it in a hogyard and along the roadside near Mauckport in 

 Harrison County and in a hogyard and an adjacent pasture and roadside 

 east of Cannelton in Perry County. 



Nat. of Eu. ; Maine to Ont. and Mo., southw. to Fla. and Tex. 



2. Xanthium pennsylvanicum Wallr. Smooth-body Cocklebur. Map 

 2108. Frequent to common throughout the state in moist places along 

 streams, about lakes, in dried-up ponds, cornfields, and cultivated grounds 

 in general. This species and the next are very annoying weeds in the 

 cornfields of the Lower Wabash Bottoms. 



Mass. to Wash., southw. to Fla., Tex., and Calif. 



3. Xanthium italicum Moretti. Hairy-body Cocklebur. Map 2109. 

 The distribution, frequency, and habitat in Indiana are the same as those 

 of the preceding species. 



Que., Sask., and Wash., southw. to W. Va. and Calif., southw. into Mex. 

 to Oaxaca, and in Eu. 



1 Wiegand says: "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 satisfactory 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." He discusses all of the Indiana forms (as I understand 

 him) except Xanthium spinosum and he refers them all to one species which he calls 

 Xanthium. orientate L. I have made a limited study of our forms in the field and I 

 have decided to treat all of our native forms under two species. Since Symons' 

 studies show that the species will hybridize, it seems best to regard our species as 

 complexes until study defines the species. The synonymy is so badly involved that it 

 is useless to repeat it. 



