i 
38 
Bulletin 71. 
Many prefer some form of the knapsack sprayer for the treat¬ 
ment of low plants. At Fig. 21 is shown one of these sprayers as 
sold by William Stahl, Quincy, Ill. Knapsack sprayers are also 
Fig. 20.—Another form of 
Air-pressure Pump. Fig. 21.— Knapsack Sprayer. 
Fig. 22.—Barrel Pump. 
made with an oil tank attached so as to spray kerosene, or petro- 
