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 
Lactica scariola, L. 
Var. integrata, Gren. & Godr. 
; Other English names: Compass Plant, 
a Milk Thistle, English Thistle. 
Fic. 373. — Spiny-leaved Introduced. Annual and winter annual. 
Sow Thistle (Sonchus asper). Propagates by seeds. 
Xa 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 hardstems 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. 
