COMPOSITAE 311 



Involucre hemispheric: heads large : achenes terete. 39. Anthemis. 

 b. Receptacle naked or sometimes merely pubescent. 

 Ray-flowers normally present. 



Involucre with several series of bracts : receptacle flat or hemispheric. 



40. Chrysanthemum. 

 Involucre with few series of bracts : receptacle conic or ovoid. 



41. Matricaria. 

 Ray-flowers wanting. 



Pappus a small crown : heads corymbose. 42. Tanacetum. 



Pappus wanting : heads spicate, racemose or panicled. 



43. Artemisia. 



Tribe VIII. SENECIONEAE. 

 Leaves of the flowering stems reduced to scales. 



Head solitary : corollas yellow. 44. Tussilago. 



Heads corymbose : corollas white or purple. 45. Petasites. 



Leaves of the flowering stems not reduced to scales. 

 Leaves opposite. 46. Arnica. 



Leaves alternate. 

 Flowers with white or pink corollas : ray-flowers wanting. 



Flowers various, the marginal pistillate, those of the disk perfect. 



47. Erechtites. 

 Flowers all perfect. 

 Involucre of about 5 main bracts. 48. Mesadenia. 



Involucre of about 12 main bracts. 49. Synosma. 



Flowers with 5-ellow corollas : ray-flowers mostly present. 



50. Senecio. 

 Tribe IX. CYNAREAE. 



Achenes inserted on the receptacle by their bases, not oblique. 

 Receptacle bristly. 

 Filaments distinct. ' 



Bracts of the involucre with hooked tips : leaves with unarmed blades. 



51. Arctium. 

 Bracts of the involucre not hooked : leaves spine-armed. 



52. Carduus. 

 Filaments united below. 53. Mariana. 



Receptacle not bristly. 54. Onopordon. 

 Achenes obliquely inserted on the receptacle. 



Heads not subtended by bristly leaves. 55. Centaur ea. 



Heads subtended by bristly leaves. 56. Cnicus 



1. VERNONIA Schreb. 

 Bracts of the involucre, at least some of them, with filiform or subulate tips. 



Pappus straw-colored. i. V. glauca. 



Pappus purple or purplish. 2. V. Noveboracensis . 



Bracts of the involucre merely acute or obtuse. 3. V. maxima. 



1. Vernonia glauca (L. ) Britton. Broad-leaved Iron-weed. 

 (Man. p. 919; I. F. f. 3604.) In woods, Pa. and Md. to Ohio, Fla. and 

 La. — Pennsylvania : Northampton ; Bucks ; Montgomery ; Dei,a- 

 WARE ; Chester ; Lancaster ; Franki,in ; Huntingdon. 



2. Vernonia Noveboracensis (L. ) Willd. New York Iron-weed. 

 (Man. p. 918; I. V. f. 3601.) In moist soil, Mass. to Minn., Ga. and 

 Kans. — Pennsylvania : Ali^EGHENy. 



