HYDRATION AND GROWTH.* 



By D. T. MacDOUGAL. 



(Read April 2$, IQIQ-) 



The studies described in the present paper are based upon the 

 results of three methods of observation and experimentation, as 

 follows : 



(a) A comprehensive series of measurements of the variations 

 in volume of stems, leaves and fruits have been made in which the 

 course of growth and variations in rate have been correlated with 

 variations in such environmental factors as temperature, humidity, 

 water supply, etc. The records include the entire developmental 

 period of many stems extending in some cases over a period of two 

 years. A paper descriptive of some of this work was presented 

 before this Society three years ago and was printed in the Proceed- 

 ings for 191 7. 



(b) Attention has been directed to the determination of the 

 composition of living matter and the manner in which its com- 

 ponents are united or mixed in the cell. Series of analyses ar- 

 ranged to show not only the general character of the cell contents, 

 but also the seasonal and developmental changes in plants have been 

 made, in connection with the comprehensive work of Dr. H. A. 

 Spoehr upon carbohydrate metabolism (now in press). 



(c) Measurements of the hydration reactions of tracts of living 

 cell-masses have been compared with the reactions of sections of 

 plates of colloids made up in simulation of the composition of plants 

 show that the water relations of the living material of the higher 

 plants are those of a colloidal mixture consisting predominantly of 

 pentosans, of a lesser proportion of albumin, albumin derivatives 

 and amino-compounds and of a minor proportion of lipins, with an 

 inevitable small amount of salts. 



The components of these three groups are not mutually inter- 

 dififusible to any extent and hence in my colloidal preparations, as 



* Abstract prepared by author from a lengthy manuscript. 



346 



