CHAPTER XIII 



EFFECT OF THE DENSITY OF THE MEDIUM 



GROWTH 



UPON 



In this chapter we cannot, as hitherto, consider the effect 

 of density upon both the rate or quantity and tlie direction of 

 growth, for no studies seem to have been made upon the latter 

 subject. 



§ 1. Effect of Density upon the Rate op Growth 



We have seen in Chapter III (p. 77) that the increase or 

 decrease in the concentration of a solution produces, by osmosis, 

 changes in the structure of protoplasm, in its locomotion, and 

 in its excretory activity. It remains to be seen to what extent 

 change in density can affect the metabolic activities concerned 

 in growth. 



The relation between the rate of growth of plants and con- 

 centration has been the subject of much study, e.g. by Wielbk 

 (■'83), DeVeies ('77), Jaeius ('86), Jentys ('88), Eschen- 

 HAGEN ('89), and Stange ('92). It is agreed that, in general, 

 as the solution containing the plant becomes more concentrated 

 the seedling or the fungus (Jentys, p. 455) grows more slowly. 



The question now arises whether there is any maximum 

 concentration at which growth is completely inhibited. Data 

 on this subject are given by Eschenhagen, who finds that 

 various fungi will not grow at a concentration above the 

 following limits : — 



362 



