254 



The Plant World. 



3 has the same treatment as No. 2 with the addition of 70 

 ccm, of NaNOg. No, 4 is growing in the untreated extract 

 plus the same amount of NaNO., as was added to No. 3. 

 The plants, as seen in the cut, show the stimulating effect 

 of the treatments. The one in the untreated extract made 

 very little growth; it is much smaller than those growing in 

 the treated solutions. 



The plants in figure 12 (at left) are the same as those 

 shown in the same figure at the right. This cut shows the 

 difference in the development of roots as well as tops. No. 



Fig. 12. Potatoes gi-owing (at right) in solution of poor soil. No. 1, untreat- 

 ed; Nos. 2, 3 and 4, variously treated. At the left the 

 same plants removed from bottles. 



2 has the best growth of roots and a healthier appearance. 

 Three bottles are used for each treatment, each serving as a 

 check on the other. 



At the conclusion of the experiment the green weight 

 of the plant is taken and the general condition of the tops 

 and roots is noted. These data, together with a photograph, 

 are used as criteria for growth. 



