10 FARM WEEDS OP CANADA 



grounds for cut-worms, and the rust of small grains may pass 

 the winter on several kinds of grasses. 



HOW WEEDS SPREAD. 



In the present age of easy communication with all parts of 

 the country, and indeed with the whole world, there are fre- 

 quent opportunities for the introduction of weed seeds into 

 previously uninfested districts. 



1. By natural agencies. The wind carries seeds long dis- 

 tances, not only in summer, but with drifting soil and over the 

 surface of the snow in winter. Streams distribute them along 

 their courses. They are also distributed by seed-eating birds 

 and herbivorous animals, through the stomachs of which the 

 seeds pass undigested; or they attach themselves by special 

 contrivances, such as hooked and barbed hairs, spines, gummy 

 excretions, etc., to passing animals. 



2. By human agencies. New weeds are introduced on farms 

 with grass, clover or other commercial seeds, and commercial 

 feeding stufifs usually contain some vital weed seeds. They are 

 spread from district to district through various transportation 

 facilities, such as railways, and become disseminated within 

 a locality in stable manure from towns and cities, and through 

 threshing machines and farm implements. The illustrations 

 of weed seeds on the last five plates of this volume will aid in 

 the identification of impurities common in commercial seeds 

 and feeding stuffs. 



CLASSIFICATION OF WEEDS. 



Weeds, like all other plants, may be classified, according 

 to the length of time they live, as annuals, or one-year plants; 

 biennials, or two-year plants; and perennials, or many-year 

 plants. In eradicating weeds, it is of the greatest importance 

 to ascertain under which of these heads they come, because 

 the treatment is usually to prevent annuals and biennials from 

 seeding and perennials from forming new leaves, roots and 

 underground stems. 



