514 COMPOSITAE (COMPOSITE FAMILY) 
Stem two to six feet tall, stout, densely white-woolly, leafy to 
the top. Leaves oblong lance-shaped in outline but deeply pin- 
natifid into triangular or lance-shaped segments, armed with long, 
stiff, yellow spines, white-woolly on the under side, sessile or 
slightly clasping, the lowest with short, margined petioles. Heads 
solitary, terminal, about two inches broad, the outer bracts of the 
involucre lance-shaped and tipped with stout, yellow spines about 
as long as themselves, the inner ones long-pointed but unarmed ; 
flowers light purple. 
Another Thistle of the plains, much resembling this one in its 
dense white-woolliness but smaller and less fiercely armed, is the 
Wavy-LEAVED THISTLE (Circium undulatum, Spreng), which has 
a wider range, extending to the Northwest Territory. 
Means of control the same as for C. lanceolatum. 
CANADA THISTLE 
Circium arvénse, Scop. 
(Cdrduus arvénsis, Robs.) 
Other English names: Creeping Thistle, Small-flowered Thistle, 
Perennial Thistle, Cursed Thistle. 
Introduced. Perennial. Propagates by seeds and by rootstocks. 
Time of bloom: June to August. 
Seed-time: July to Septemher. 
Range: Newfoundland to the northwest provinces and British 
Columbia, southward to Virginia and Kansas. 
Habitat: Cultivated fields, meadows, pastures, roadsides, and 
waste places. 
In 1896 the United States Department of Agriculture published 
a bulletin, “Legislation against Weeds,’ compiling the acts then 
on the statute-books of the several states and recommending a 
general state weed law, sufficiently elastic to fit the varying flora, 
soils, and climate. Therein it is shown that all but three of the 
states having laws for the suppression of weeds make it an offense 
for their citizens to permit the Canada Thistle to mature and 
sedtter its seeds. Penalties are also provided in the case of seeds- 
men who sell grain, grass, or clover seeds contaminated by its 
presence — but the thistle marches on, bidding defiance in every 
