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. 



16. SONCHUS L. SOW-THISTLE; MILK-THISTLE. 



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



Involucres glabrous; heads about 15 mm. high. 



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



Auricles of the leaves rounded ; achenes not transversely wrinkled. 



3. S. asper. 



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

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



2. 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. 



