COMPOSITAE (COMPOSITE FAMILY) 539 
smooth, green, hollow between nodes, filled with milky juice. Leaves 
lyrate-pinnatifid, the terminal lobe large and triangular, the others 
narrow and decreasing in size toward 
the base; the lower and basal leaves 
petioled, but those on the stem clasping 
with an auricled and pointed base; the 
margins toothed with small, weak 
spines. Heads in crowded cymose 
panicles, yellow, nearly an inch broad; 
the involucres are downy while they 
enclose the buds, but later become 
smooth. Achenes brown, slightly flat- 
tened, with roughened ribs and thickly 
tufted, white, silken pappus. (Fig. 
372.) 
Means of control 
Prevent seed development. In gar- 
dens and other small areas, hand-pull 
before the first flowers mature. Stub- 
bles should have surface cultivation 
after harvest for the purpose of stirring 
into life such seeds as are on the ground, 
Fic. 372. Common Sow 
Thistle (Sonchus oleraceus). 
xt 
the seedlings to be turned under at fall plowing. Waste places 
and roadsides are too often permitted to mature seeds, to the 
damage of adjacent ground. 
SPINY-LEAVED SOW THISTLE 
Sénchus dsper, Hill 
Introduced. Annual. Propagates by seeds. 
Time of bloom: May to October. 
Seed-time: June to November. 
Range: All cultivated parts of the world. 
Habitat: Fields, roadsides, waste places. 
More prickly than the preceding species ; 
the spines, though weak 
compared with those of true thistles, can make themselves felt 
when touched, while those of the Hare’s Lettuce are too soft to pene- 
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