CICHORIACEAE. 411 



6. Lactuca spicata (Lam.) Hitchk. (L. leucophaea A. Gray) In moist 

 ground from Newf. and Man. to N. C. and Colo. — Boulder; Steamboat 

 Springs. 



i6. SONCHUS L. Sow-thistle; Milk-thistle. 



Involucres glandular-pubescent; heads about 25 mm. high. i. 6'. arvensis. 



Involucres glabrous ; heads about 1 5 mm. high. 



Auricles of the leaves acute ; achenes transversely wrinkled. 2. 5". oleraceus. 



Auricles of the leaves rounded ; achenes not transversely wrinkled. 



3. 3'. asper. 



I. Sonchus arvensis L. In fields from^Newf. and Minn, to N. J. and Colo.; 

 also on the Pacific Coast; introduced from Europe. — Walsenburg. 



z. Sonchus oleraceus L. In fields and waste places from N. S. and Wash, 

 to Fla. and Calif. ; introduced from Europe. — Alt. 5000 ft. — Ft. Collins. 



3. Sonchus asper (L.) All. In waste places and fields from N. S. and B. C. 

 to Fla. and Calif. ; introduced from Europe. — Alt. 4000-8000 ft. — Along Un- 

 compahgre River, near Ouray; Cerro Summit; Glenwood Springs. 



