308 COMPOSITAE 



B. Plants not spine-armed : leaf-blades of a reniform, orbicular or ovate type, 

 cordate or truncate. 

 Mature pistillate involucre 12-20 mm. long, glabrous or nearly so, with 



straight or nearly straight beaks. 2. X. glabratum. 



Mature pistillate involucre 15-30 mm. long. 

 Body of the bur-like involucre oblong, twice as long as thick or more. 



3. X. Pennsylvanicum. 

 Body of the bur-like involucre ovoid or oval, less than twice as long as 

 thick. 4. X. echinaium. 



1. Xanthiiiin spinosum L. Spiny or Thorny Clotbur. (Man. 

 p. 912 ; I. F. f. 35gS.) In waste grounds. Out. to Fla., west to W. Va., 

 Mo. and Tex. Nat. from Eu. and Asia. — Pennsylvania : Northamp- 

 ton ; Bucks ; Phii,adei,phia ; Delaware ; Chester ; Lancaster ; 

 York; Franklin. 



2. Xanthium glabratum (DC.) Britton. SmooThish CocklEbur or 

 BuRWEED. (Man. p. 912 ; I. F.y. J599.) In waste places, N. Eng. to Fla., 

 Neb. and Mex. — Pennsylvania : Northampton ; Bucks ; Delaware ; 

 Chester ; Lancaster ; Franklin ; Allegheny. 



3. Xanthium Pennsylvanicum Wallr. Pennsylvania CloTbur. 

 (Man. p. 912.) In open places, Ont. to D. C. and Minn. — Pennsyl- 

 vania : Northampton ; Erie. 



4. Xanthium eohinatum Murr. Beach Clotbur. (Man. p. 913.) 

 On river shores, lake and sea beaches, Vt. to Minn, and N. C. — Penn- 

 sylvania : Northampton. 



Family 5. COMPOSITAE Adans. Thistle Family. 



Stigmatic lines at the base of the stigfma or below the middle. 

 Stigmas filiform or subulate, hispidulous. Tribe I. VERNONIEAB. 



Stigmas more or less clavate, papillose-puberulent. 



Tribe II. EUPATORIEAE. 

 Stigmatic lines extending to the tip of the stigma or to the appendages, 

 a. Anthers without elongated appendages at the top. 

 Anther-sacs tailed at the base. Tribe IV. INULEAE. 



Anther-sacs not tailed at the base. 

 Receptacle naked. 

 Bracts of the involucre well imbricated. 

 Stigmas of the perfect flowers with terminal appendages. 



Tribe III. ASTEREAB. 

 Stigmas of the perfect flowers with truncate or hairy or papillose tips. 

 Bracts of the involucre herbaceous. 



Tribe VI. HELENIEAE. 

 Bracts of the involucre dry and scarious. 



Tribe VII. ANTHEMIDBAE- 

 Bracts of the involucre little if at all imbricated, except when the 

 broad outer ones overlap the inner. 



Tribe VIII. SENECIONEAE. 

 Receptacle chaffy. 

 Bracts of the involucre herbaceous, sometimes foliaceous. 



Tribe V. HELIANTHEAE 

 Bracts of the involucre dry and scarious. 



Tribe VII. ANTHEMIDBAE. 



