340 COMPOvSITAE 



to Va., west to Minn, and Mich. Also on Pacific coast. Nat. from Eu. 

 — Pennsylvania : Phii^adelphia ; Monroe, Tobyhanna ; Franklin. 



6. Senecio sylvaticus L. Wood Groundsel. (Man. p. 1029 ; I. F. 

 f. 40j2. ) In waste places, N. S. and Prince Edward Island. Also on the 

 coast of Calif, and B. C. Nat. or adv. from Eu. — Pennsylvania : Phila- 

 delphia, ballast. 



7. Senecio viscosus L. Fetid or Viscous Groundsel. (Man. p. 

 1029; I. F. y; 405^.) In waste places and on ballast near the coast, N. B. 

 to N. C. — Pennsylvania : Philadelphia, ballast. 



51. ARCTIUM L. 

 Bracts of the involucre glabrous or nearly so. i. A. minus. 



Bracts of the involucre copiously wooll3-. 2. A. tomentosunt. 



1. Arctium minus Schk. Common. Burdock. (Man. p. 1030; I. 

 'F.f.40^7.) In waste places, throughout eastern North America. Nat. 

 from Eu. — Pennsylvania : Common throughout the State. 



2. Arctium tomentosum (Lam.) Schk. Woolly or Cottony Bur- 

 dock. (Man. p. 1030; I. F. y. 40j^.) In waste places, N. B. to Mass. 

 and southern N. Y. Adv. from Eu. — Pennsylvania : Delaware. 



52. CARDUUS L. 



Pappus-bristles, at least those of the inner flowers, plumose. 



Bracts of the involucre, at least the outer ones, strongly prickle-armed. 

 Leaves glabrous or hispid above, tomenlose beneath. 

 Outer and inner bracts of the involucre prickle-armed : naturalized plant. 



I. C. lanceolatus. 

 Outer bracts of the involucre prickle-armed, the inner merely acumi- 

 nate : native plants. 

 L,eaf-blades toothed or pinnately lobed. 2. C. allissimus. 



Leaf-blades deeply pinnatifid. 3. C. discolor. 



Leaves green on both sides, or somewhat pubescent beneath. 



4. C. odoratus. 

 Bracts of the involucre not prickle-tipped or scarcely so. 



Heads relatively large : involucre about 2 cm. thick or more : flowers per- 

 fect and fruit producing. 

 Heads sessile in an involucre of ver3' spiny bracts. 5. C. spinosissivius. 

 Heads peduncled, not involucrate. 6. C. viulicus. 



Heads relatively small : involucre about 1 cm. thick : flowers dioecious. 



7. C. arvensis. 

 Pappus-bristles smooth or minutely serrulate. 



Head solitary, nodding : bracts of the involucre lanceolate. 



8. C. nutans. 

 Head clustered, erect or ascending : bracts of the involucre linear. 



9. C. crispus. 



1. Carduus lanceolatus L. Common Bur or Spear Thistle. (Man. 

 p. 1031 ; 1. F. y; 405S.) In fields and waste places, Newf. to Ga., west to 

 Minn., Neb. and Mo. Nat. from Europe. Nat. also from Asia. — Pemi' 

 sylvania : Lackawanna ; Monroe ; Northampton ; Bucks ; Dela- 

 ware ; Chester ; Lancaster ; Franklin ; Huntingdon ; Alle- 

 gheny. 



