COMPOSITAE (COMPOSITE FAMILY) 461 
pistil with its cleft style slightly exserted from a hairy and 
spiny involucre which later becomes a bur about a_half- 
‘inch long, with two straight beaks at apex and a covering of 
short, smooth, hooked spines. The burs are two-celled, each cav- 
ity containing a thick-coated, dark brown, flattened seed. 
Means of control 
In pastures and meadows the plants should be watched for and 
cut off in May or June with a sharp hoe or spud; some will be over- 
looked, to appear conspicuously later, bristling with spines and 
burs; these should be cut, piled to dry for a few days, and burned. 
In cultivated ground tillage should be continued late in order to 
prevent the development of seed from late-blooming flowers. 
CLOTBUR 
Xdnthium canadénse, Mill. 
Other English names: Cocklebur, Sheepbur, Buttonbur, Ditchbur, 
Hedgehog Burweed. 
Native. Annual. Propagates by seeds. 
Time of bloom: July to September. 
Seed-time: September to November. 
Range: Nova Scotia to the Northwest Territory, southward to 
Texas and Mexico. Abundant on the Pacific Coast. 
Habitat: Rich, moist soil; cultivated crops, barnyards, roadsides, 
and waste places. 
A huge, coarse plant, one to four feet tall, branched, and widely 
spreading, its rough, thick, angled stem often reddish and spotted 
with brown. Leaves also bristly rough on both sides, alternate, 
large, broadly oval to heart-shaped, with toothed edges, strongly 
three-nerved and often three-lobed, with long, rigid petioles, often 
reddish like the stem and contrasting with the dark green of the 
leaf surface. The sterile heads are clustered at the ends of the 
branches, small, greenish, and inconspicuous, resembling those 
of Ragweed; below, in the axils, the fertile heads are densely 
clustered ; these are thick, green, oblong, densely hairy, and spiny 
involucres, from which is thrust a style with two-parted stigma; 
these involucres develop into burs nearly an inch long, with a 
