COMPOSITAE THISTLE FAMILY BULL THISTLE 799 



Fig. 456. Canada Thistle (Cirsium arrense). Common in the North, causes inflamma- 

 tion. (Charlotte M. King). 



decurrent on the stem with prickly wings, deeply pinnatifid, the lobes with rigid 

 prickly points, upper face roughened with short hairs, lower face with cottony 

 tomentum; heads 1^4 to 2 inches high, bracts of the involucre lanceolate, rigid 

 when young, more flexible with age, long attenuated prickly pointed spreading 

 tips, arachnoid woolly; flowers perfect; anther tips acute; filaments pubescent; 

 achenes smooth; pappus of numerous plumose bristles. 



Distribution. Distribution in North America in fields and waste places 

 from Newfoundland to Georgia, Missouri, Kansas to Nebraska, the Dakotas, 

 Montana, Washington, Oregon and Idaho. Naturalized from Europe, native 

 also to Asia. 



