Hydration and Growth of Colloids and Cell-masses. 127 



under acid conditions, as has been demonstrated both in sections of 

 pentosan-protein biocoUoids and in living and dried sections of plants. 

 The application of a temperature coeflElcient derived from a simple 

 equation to the rates of growth of organs of green plants has a certain 

 practical value when temperatures between the minimum and the 

 maximum rate are under consideration. As changes in temperature 

 affect a number of constituent processes in growth, including absorp- 

 tion and diffusion, transpiration, adsorption, action of acidity or 

 hydrogen-ion concentration, formation of the amino-acids, enzymic 

 action and oxidations, and all transformations of the carbohydrates, 

 the empirical character of such indices must be kept well in mind. 

 The character of temperature coefficients is sufficiently indicated by 

 the fact that they are not found to apply through the range of practi- 

 cable or habitual conditions of the organism and that the values change 

 within the range of 8° to 30° C. when falling and rising temperatures 

 are contrasted. 



