314 FLORA OF PHILADELPHIA. 



2. Xanthium glabratum (DC.) Britton. M. p. 912. Waste grounds. 



Autumn. 



3. Xanthium Pennsylvanicum Wallr. Open places. Autumn. 



Northampton — (P.) . 



4. Xanthium Canadense Mill. M. p. 912. Waste ground. Autumn. 



Delaware — Upper Darby, Chad's Ford (B. Sni.). 



5. Xanthium commune Britton. M. p. 912. Waste ground. Autumn. 



Delaware — Upper Darby (B. Sm.). 



6. Xanthium echinatum Murr. M. p. 913. Eiver shores, sea-beaches and 



waste places. Autumn. 



.! Family 5. COMPOSITAE. Thistle Family. 



Anthers not tailed at the base; stigmatic lines of the style-branches only at 

 the base, or not extending beyond the middle; flowers all tubular and 

 perfect, never yellow ; rays none. 

 Style branches filiform or subulate, hispidulous; receptacle naked. 



Tribe 1. Fernonieae. 

 Style branches thickened upward, obtuse, papillose. 



Tribe 2. Eupatorieae. 

 Anthers tailed at the base, unappendaged at the tip; heads small; rays none 

 . (except in Inula, where they are large and yellow). 



Tribe 4. Inuleae. 

 Anthers not tailed at the base ; stigmatic lines of the style-branches in the 

 ■■ perfect flowers extending to the summit; flowers tubular only, or 



tubular and radiate, often yellow. 



1. Beceptacle naJied (see also No. 39 of Tribe 6). 



a. Bracts of the involucre usually well imbricated. 



Style branches of the perfect flowers flattened, with terminal ap- 

 pendages. Tribe 3. Astereae. 

 Style-branches truncate, or with hairy tips. 



Bracts of the involucre herbaceous. Tribe 6. Helenieae. 

 Bracts of the involucre dry and scarious. 



Tribe 7. AntJiemideae. 

 h. Bracts little imbricated or not at all; j^appus of soft bristles. 



Tribe 8. Senecioneae. 



2. Heceptacle cliafy. 



Bracts of involucre herbaceous or f oliaceous ; not scarious. 



Tribe 5. Heliantheae. 

 Bracts of the involucre dry, scarious. Tribe 7. Anthemideae. 



Anthers long-tailed at the base, with elongated appendages at the tip ; heads 

 large; rays none. (In Centaurea often with enlarged marginal flowers; 

 bracts imbricated.) Tribe 9. Cynareae. 



Tribe 1. VERNONIEAE. 



Pappus double; heads not glomerate. 1. Vernonia. 



Pappus a single series of bristles ; heads glomerate. 2. Elephantopus. 



Tribe 2. EUPATORIEAE. 



Achenes 3-5-angled, not ribbed. 



Pappus of 5 broad, obtuse scales ; aquatic herb with linear-whorled 



leaves. 3. Sclerolepis. 



Pappus of numerous capillary bristles. 



Involucre of more than 4 bracts; erect herbs. 4. Eupatorium. 



