256 J. J. SKINNER 



In another experiment conducted at a different time essen- 

 tially the same results were obtained. The solanine again being 

 dissolved by heating as before. The plants grew from June 13 

 to July 15. The solutions were changed as before, every three 

 days. The weights of the three plants in the soil extract control 

 was 2.72 and the corresponding solanine cultures were 1.98 grams. 

 The soil extract from another soil gave 2.88 grams and the corre- 



TABLE 1. 

 Effect of solanine on the growth of potatoes. 



Green weight of 



3 cultures. 



Grams. 



Extract of good potato soil, boiled, 6 . 82 



Extract of good potato soil, boiled + solanine 2.33 



Extract of poor potato soil, boiled, 4.60 



Extract of poor potato soil, boiled + solanine 1.83 



sponding solanine cultures 1.35 grams. In this experiment as well 

 as the others given in this paper, the roots of the plants were also 

 injured by the solanine. The roots in the solanine cultures did 

 not develop and branch as they did in the control cultures. 



Although solanine is a constituent of potatoes, it is apparent 

 from these experiments, in which distilled water and soil extract 

 were used as the culture solutions, that it is harmful to the growth 

 of the potato plant, when presented in a culture solution. 



