4 WEEDS OF THE FARM AND GARDEN 



much more exhaustive than others. We need conserva- 

 tion of the fertility of soil by preventing the growth of 

 weeds. 



Another reason why weeds are injurious, especially to 

 young crops, is because they crowd out the useful plants. 

 This is particularly true of such weeds as nut grass in 

 our cornfields, mustard, at times, in oats and flax fields. 



Some weeds are injurious because they are poisonous 

 to man and the lower animals. Cowbane and water pars- 

 nip are powerfully poisonous ; the seed of corn cockle 

 poisons grain ; squirrel-tail, wild barley and awned brome 

 grass are injurious because the awns work into the gums, 

 causing serious inflammation and consequent loss of 

 teeth. 



Weeds are injurious because, on account of their pres- 

 ence, it is much harder to remove the crop. It is much 

 more difficult to harvest wheat where Russian thistle is 

 present. It is much more difficult to harvest small grain 

 where wild buckwheat and morning glory occur. The 

 spines of rose stems often inflict injury to persons obliged 

 to shock and stack grain. 



V Weeds are frequently injurious because they harbor 

 \ fungi. The well-known club root of cabbage occurs on 

 mustard and on other allied plants ; also on common pepper 

 grass, and Dr. Halsted has shown that this is a frequent source 

 of the disease on cabbage. Rust is often found on squirrel- 

 tail grass. Professor Bolley says : " Weeds, because 

 of their rank foliage, tend to keep the atmosphere cooler 

 and moist, keeping the stems and foliage of the grain 

 plants befogged with dew and other moisture when or- 

 dinarily it would remain comparatively dry. This ac- 

 counts for the rust getting a stronger infection in the 

 wheat fields than upon a clean, open crop. Later, when 

 the grain is strongly attacked by the rust fungus and is in 

 great need of water to keep up the supply which is being 

 evaporated from the straw or stems where the rust has 



