I04 



BOTANICAL GAZETTE 



[august 



experiments were continued long enough to insure the satura- 

 tion of the water at these pressures, which in the case of Og takes 



about a couple of weeks. 



The results of the experiments were that in every case the 

 water form was produced. This shows that the lack of CO^, at 



Fig. 9 — Plants grown first in water, then in air, then in water, then in air. 



least, cannot be involved in the stimulus to the formation of the 

 water form, for the amount that diffused into the plant was, at 

 least in the one case, certainly greater than that which it gets 

 from the normal atmosphere. Of course it is possible that the 



r 



large amount might induce abnormal or pathological changes 

 which would prevent the normal development, but the two smaller 

 quantities produced the same results. While an increased pres- 

 sure of five times the normal O^ pressure still results in the water 

 form, it is possible that still higher pressure might act differently. 

 This is not probable, however, for two reasons: (i) the plants 



