they rob the succeeding crop as well. For example, an analysis of the 

 Russian Thistle by Snyder showed " that it contains from 12 to 17 

 per cent, as much nitrogen as there is in clover ; and an ordinary 

 thistle of this kind covering a square yard takes more potash and lime 

 from the soil than two good crops of wheat from the same area." 



3. They shade, crowd, and choke useful 2)la'nts. Weeds often 

 grow more vigorously than useful plants; and, as a consequence, they 

 shade, or crowd, or partially choke the seedlings of the desiied crop. 

 'Black Bindweed (Fig. 20), for instance, often covers completely a large 

 part of the plants among which it grows. 



4 They increase the labour and expense of cleanivg seed. At 

 best, it is difficult to clean many of the smaller seeds, such as clover, 

 grass, and rape seed ; and the difficulty is greatlj^ increased when they 

 are grown on a dirty farm. It is almost impossible to clean clover 

 seed by winnowing. Hence the necessity that the land on which it 

 grows be clean. 



5. TJiey interfere unth a regular rotation of crops. A well 

 balanced rotation of crops conserves the fertility of the soil ; but it is 

 often necessary to depart from such a rotation when noxious weeds 

 get possession of the farm— to give undue attention to the growth of 

 hoed crops, for instance, or alm< st omit a certain crop altogether for 

 a time, as in the case of the oat crop on a farm overrun with wild oats. 



6. They harbor' the spores of injurious fungi Many of the 

 rusts which attack grain crops tind a resting place on weeds of the 

 grass and other families, which preserve them through the fall, winter, 

 and spring. 



7. Lastly, they of end the eye, or are, as we say, an eyesore to good 

 farmers and all people of taste. The> also intei fere with the use of 

 mowers, binders, and other implements in taking oft' crops. 



Introduction and Spread of Weeds. 



Most of the injurious weeds found in this Province have come 

 directly or indirectly from other countries. They are brought in and 

 conveyed from tield to tield and farm to farm in various ways : , 



1. By the wind. Seeds which are carried by the wind usually 

 have tufts of fine silky hair attached to them. Such are the seeds of 

 the Dandelion, Canada Thistle, Sow Thistle (annual and perennial). 

 Willow Herb, and Cotton Grass. These and f^imilar seeds are wafted 

 to and fro, till they become attached to the soil and commence to 

 grow. In some cases, as in the Dock and Wild Parsnip, the seeds are 

 winged ; in others the pod containing the seed has flat and extended 

 edges, exposing much surface to the wind. The Penny Cress is an 

 example of the latter. 



Some weeds are rolled along the ground by the wind. To this 

 .class belong the Russian Thistle and the Tumbling weed of the North- 



