48 



THE MONTHLY BULLETIN. 



CANADA THISTLE. 

 (Girsium arvensis.) 



By O. W. Newman. 



The Canada thistle is just becoming established in California, and 

 the time to eradicate it is now, before it becomes a well established 

 resident with us. Infestations have been reported from Humboldt. 

 Lake and Orange counties; these counties are located respectively in 

 the northern, north central, and southern parts of the state, providing 



Fig. 



10. Canada Thistle, Ciraium arvensis, showing the leaves and 

 flowers. (After Clark and Fletcher.) 



three excellent centers from which to distribute the pest. The state 

 commission of horticulture has been directing attention to one of these 

 areas of infestation for the last two years; the other two have only 

 recently been reported. In view of the present widespread interest in 

 weed control we seize the opportunity to inform the public of this most 

 noxious pest, that its spread may be cheeked. 



