AUG 8 19)7 



GROWTH AND IMBIBITION. 



By D. T. AIACDOUGAL, Ph.D., LL.D., axd H. A. SPOEHR, Ph.D. 

 (Read April 13, 1917-) 



General Considerations. 



The chief purpose of the studies described in the present paper 

 has been to correlate some of the more striking features of growth 

 in plants with the action of contributory factors, and to resolve this 

 complex process into its constituent reactions so far as might be 

 possible. 



New viewpoints have been sought by the reduction and analyses 

 of continuous series of measurements of the entire course of 

 enlargement of single organs or members. Experimental species 

 were chosen concerning which much was known as to their respira- 

 tion, transpiration, imbibition capacity and chemical composition. 

 The daily, seasonal and developmental variations in such matters as 

 carbohydrate content, acidity and swelling capacity of some of the 

 plants had already been the subject of various investigations at the 

 Desert Laboratory, and additional determinations were made in the 

 course of the work. The final or actual increase which is measur- 

 able as growth, by weight or dimensions is predominantly a hydra- 

 tion or imbibition process as the increment to any growing cell or 

 embryonic region is at least 99 per cent, water. There is immediate 

 necessity therefore for a study of factors influencing imbibition. 

 Whatever theory of colloidal structure may be adopted, there is no 

 reason for supposing that the interpolation or absorption of water in 

 a complex mixture of such substances is different in the plant cell 

 from what it might be in similar material in the laboratory. The 

 protoplast and its envelopes are undoubtedly a complicated mixture 

 of colloids in a state of more or less constant change. 



A 'successful search was instituted for mixtures which would 

 show the same general imbibition phenomena as the living plant. 



PROC. AMER. PHIL. SOC, VOL. LVI, T, JULY 30, I917. 



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