193 



tbe first year — and aerial stems the secoud year. The plant appears to 

 die at the end of the second summer ; bnt it only dies down to the hori- 

 zontal subterranean stem. The numerons branches sent up from the rhi- 

 zoma, soon cover the ground with the prickly radical leaves of the plant : 

 and thus prevent cattle from feeding where they are. Xothing short of 

 destroying the perennial portion of the plant will rid the ground of this 

 pest ; and this, I believe, has been accomplished by a few years of con- 

 tinued culture (or annual cropping of other plants, that require frequent 

 ploughing, or dressing with the hoe,) — so as to prevent the development 



Fig. 134. The Canada Thistle (Qrsium arvense), reduced. 



