248 



WEEDS OF THE FARM AND GARDEN 



teen inches long, deeply pinnatifid, the divisions fre- 

 quently divided, prickly toothed, the upper surface 

 smoothish and the lower white and woolly, finely divided 

 stem leaves; single heads one and one-half inches 

 long with purple flowers terminating the branches ; bracts 

 of the involucre somewhat appressed, slightly weblike ; 

 lower bracts ovate with a broad base and a weak, prickly, re- 

 curved bristle, slight dorsal gland ; inner bracts, linear-lanceo- 

 late, with an entire, nearly colorless appendage; flow- 

 ers ourple, the lobes terminating in cleft tips; anther 



tips acute, filament pubescent; 

 bristles of pappus plumose, 

 achene smooth, upper part yel- 

 low. On roadsides and in mead- 

 ows from New Brunswick west- 

 ward to Ontario, Minnesota and 

 Iowa. 



Canada Thistle (Cirsium ar- 

 vense, (L.) Scop.). A smooth 

 perennial, spreading by creeping 

 rootstocks ; corymbosely 

 branched at the top, growing 

 one to three feet high, smooth ; 



leaves lanceolate, sessile, and 

 Fig. 158. Bull thistle (Cir- . ./. , 



slum ^ lanceolatum). Com- deeply pinnatifid, the lobes and 

 mon in pasture, wood lots margins of the leaves being be- 

 and roadsides. (Ada Hay- ,> .-, i < 



den ^ set with spiny teeth ; heads 



small, three-fourths to one inch 



high, bracts pressed closely to head, the outer with a 

 broad base, the inner narrow, all with an acute, never 

 spiny tip ; flowers purple, dioecious ; all the bristles of 

 the pappus plumose. 



The chief points of difference between the Canada 

 thistle and other allied species are as follows : the head is 

 smaller, the involucre or modified leaves surrounding the 

 head is not spiny, but smooth; the leaves are lance- 



