34 



ASTERACEAE 



(b) Heads in flat-topped clusters, or single 

 x. Involucrai scales dry and papery, yellow to white or red 

 (x) Leaves white-cottony, extending along the stem as wi 

 (y) Leaves not white-cottony, stem not winged 

 }■ Involucrai Males not papery, usually green 

 (x) Heads white, yellowish or purplish; native 

 in. Heads whit.-, pink or purplish 

 n. Heads yellowish 

 (y) Heads deep purple or blue 

 m. Heads deep purple; native 

 n. Heads blue, rarely white; cultivated 

 b. Flowers greenish; heads inconspicuous 



(1) Leaves broad, ovale, not deeply lobed 



(a) Involucre forming a hooked bur 



(b) Involucre not hooked 



(2) Leaves narrow or deeply lobed 

 (a) Leaves strong-scented" 



x. Pappus a short crown 



Ammobium 

 Helichrysum 



Eupatoriu, 



Kuhnia 



Vernon'ia 



Age vat um 



Xanthium 



Iva 



Tanaceium 



te head of Cosmos with long sectior 



ray flower and tubular or disk flower. 



