540 



COMPOSITAE (COMPOSITE FAMILY) 



trate the skin. Stems one to six feet 

 high, smooth, angled, branching, full of 

 milky sap. Lower leaves sometimes 

 pinnatifid but usually undivided and 

 spatulate, tapering to margined petioles ; 

 stem-leaves oblong or lance-shaped, 

 clasping the stem with rounded auri- 

 cles, the margins prickly-toothed, the 

 surfaces dark green, smooth, and shin- 

 ing. Heads similar to those of the 

 Common Sow Thistle. Achenes oblong, 

 compressed, margined, with smooth ribs. 

 (Fig. 373.) 



Means of control the same as for 

 Common Sow Thistle. 



PRICKLY LETTUCE 



Lactuca scarwla, L. 

 Var. integrata, Gren. & Godr. 



Other English names: Compass Plant, 



Milk Thistle, English Thistle. 

 Introduced. Annual and winter annual. 



Propagates by seeds. 

 Time of bloom : July to October. 

 Seed-time: August to November. 



Range: Massachusetts to Georgia and Tennessee, westward to the 

 Missouri River ; also in Idaho, Oregon, and Washington. Most 

 abundant in the Ohio Valley and in the states bordering on the 

 Great Lakes. 

 Habitat : All soils ; invades all crops. 



A noxious weed that owes its wide range almost entirely to the 

 agency of impure seed. It first appeared in Massachusetts not 

 many years ago, and has since journeyed from ocean to ocean and 

 could probably be found now in every state in the Union. In 

 addition to its robbery of the crop in grain fields, the hard stems dull 

 the reaping knives, and the copious, milky juice makes the weed 

 very troublesome in threshing machines when handling a crop im- 

 mediately after the reaping, without drying in the shock, as is 

 frequently done in the "West. 



FIG. 373. Spiny-leaved 

 Sow Thistle (Sonchus asper). 



