204 



EXPERIMENT STATION BULLETIN. 



Mr /w 



Fig. 219 (191). 



Canada Thistle. Cirsium arvense (L.) Scop. (Carduus arvensis (L.) Robs.) A 

 slender, nearly smooth perennial, 30-90 cm. high from extensively creeping rootstocks; 

 leaves narrow, the margins bending irregularly up and down, backward and forward, 

 each lobe always terminating in a sharp stiff point; flowers rose purple or whitish; 

 scales of the heads not bristly pointed; each seed as it grows usually produces a male 

 plant or a female plant; by rootstocks a half acre or more is often the result of a single 

 seed. 



