THE PARASITES OF PLANTS 



57 



Fungous Parasites. The fungous parasites are often 

 quite as harmful as injurious insects. The blight of the 

 pear tree, the smutted heads of 

 grain (Figure 26), the rotting 

 plums and cherries on the 

 trees and grapes on the vines, 

 are examples of plant diseases 

 due to injurious fungi. We 

 have learned to prevent some 

 of the injuries caused by 

 fungi. It is usually important 

 to apply our preventive before 

 the disease appears, otherwise 

 it may come too late to be 

 helpful. An ounce of preven- 

 tion is worth a pound of cure. 



Bordeaux Mixture. To pre- 

 vent harmful fungi, the so- 

 called "Bordeaux mixture" 

 is most used. To make this, 

 put five gallons of water into a 



wooden vessel holding at least twelve gallons, and in 

 this water hang a cloth sack containing one pound of 

 copper sulfate (also called bluestone and blue vitriol). 

 (Figure 27.) In another wooden vessel, slack one pound 

 of fresh quicklime in five gallons of water. When the 

 copper sulfate has all dissolved, and the lime has all 

 slacked, stir up the lime and water and strain the mixture 

 slowly through a coarse cloth into the copper sulfate solu- 

 tion. The coarse part that will not go through the cloth 

 may be thrown away. The mixture is best put on the 



FIG. 26. Heads of oats affected 

 with smut. Reduced one-half. 



