62 HANDBOOK OF NATURE STUDY 



The Canada thistle is a perennial, which means that its 

 roots live in the ground from year to year. In spring these 

 roots send out shoots, or rootstocks, in all directions. A 

 single plant can spread over a square rod in two or three years 

 by its rootstocks alone. This is the reason that the weed 

 is so difficult to eradicate. Every owner of land should 

 see that it does not become firmly established. Frequent 

 grubbing or mowing, ploughing several times in August, 

 salting the plants and then pasturing sheep on them, 

 applications of kerosene and carbolic acid, are all recom- 

 mended as means to kill the Canada Thistle. About the 

 detail of those measures consult your State Reports or 

 Bulletin No. 39 of the Wisconsin Agricultural Experiment 

 Station. 



No. 6. The Burdock. 



The Burdock is another common weed, too well known 

 to need any description here. In size it rivals the giant 

 ragweed and the false sunflower. It is not troublesome 

 on cultivated land, but takes possession of every corner 

 of rich soil, where a lazy and careless owner leaves it 

 undisturbed. What makes it a nuisance? Can you tell 

 to which family it belongs ? 



This weed is a biennial, which means that it lives two 

 seasons or summers. 



The seeds germinate generally the spring after they 

 matured. During the first summer the plant simply pro- 

 duces a whirl of large leaves and a strong root, but no 

 stem. This root lives through the winter, and in the 

 following spring, the second in the life of the plant, pro- 

 duces leaves, a branched stem, and a large number of flower 

 heads. When the seeds have matured, these heads form 



Observations. What becomes of house flies, wasps, and mosquitoes in 

 late autumn? 



