56 ILLINOIS ACADEMY OF SCIENCE 



activity at its optimum. The elongation is of course temporary 

 for the high concentration of acid soon proves fatal. Lower 

 concentrations of acid increase the rate of elongation, but less 

 considerably and for a longer period. There seems to be evi- 

 dence for the view that rate of growth in plants is regulated 

 to a considerable degree by organic acids formed (15, 16, 18). 

 Whether this is due in the main to the hydration effect of the 

 H+, or whether the acids also favor the formation and activa- 

 tion of enzymes, or perhaps other processes are effective, is 

 not established. 



Acids and bases increase the rate of water absorption by 

 seeds and they are good forcing agents for many seeds (16, 

 17, 18). This forcing effect in some cases is due to increased 

 water absorption by the seed coat. In other seeds the reagents 

 have this and other effects upon the embryos. I shall be 

 surprised if the often mentioned forcing powers of neutral 

 salts for seeds is not due in many cases to its effect upon water 

 absorption by gels of the seed coats and the endosperm. Assum- 

 ing that these gels are electro-negative one would expect such 

 salts as lithium, sodium and potassium chlorate, nitrate or 

 chloride to increase water absorption while salts involving 

 calcium or sulphate might have the opposite effect. 



As yet, however, we know very little about the role of these 

 reagents in water absorption by carbohydrate gels, which are 

 so prominent in seed coats. There are peculiar cases (19) 

 recorded, such as the power of potassium salts to increase the 

 water absorption and cause the final dissolution of the cell 

 walls in the growing zone of roots. 



Calcium salts alone or in combination with other salts on 

 the other hand, maintain the proper consistency of the walls 

 and integrity of the roots. In fact Cranner finds that in gen- 

 eral potassium salts greatly favor the absorption of water by 

 cell walls and inhibit the evaporation of water from them; 

 while calcium salts have the opposite effect. The effect of these 

 salts upon water absorption and retention by the cell wall is 

 similar to their effect upon transpiration which indicates that 

 they modify the latter process, at least in part and perhaps in 

 the main, quite independent of the protoplasm. 



Calcium ions tend to maintain the proper consistency of the 

 intracellular cements of animal cells, while potassium ions lead 

 to their dissolution ( 1 ) . 



In this connection we should mention certain effects of cal- 

 cium and other bivalent and even trivalent ions upon the 

 protoplasm. They reduce the permeability of the protoplasm 



