[Chap. XXIII PLANT BEHAVIOR RELATED TO OSMOSIS 



211 



^«,w-^. , . y iig-l 



lyx ..■■;»''*5sS&\' t. ' 



wtgsy -U* ■» ' J* ' '" '""g ' f 





Fig. 71. Hummocks of pickleweed (AUenrolfea) on salt-Hats in Utah. Plioto by 



H. L. Shantz. 



living cells. This coagulative effect of acetic acid may be demonstrated 

 by pouring a little vinegar on the "white" of an uncooked egg, or by 

 examining living cells mounted in vinegar. The killing effect of many 

 kinds of acids and salts should be attributed not to physiological drought, 

 but to some other condition such as the coagulation of protoplasm, altera- 

 tions in penneabilitv, or inactivation of enzymes. For example, the small 

 amount of copper sulfate or mercuric chloride necessary to kill plant 

 cells has little influence on the concentration of the water in which these 

 salts are dissolved. 



Enlargement of cells during growth. In all growing regions of a plant 

 cell division is usually followed by an increase in size of the young cells. 

 The volume of these newly formed cells may increase many times ( Fig. 

 31, page 64). 



Some new protoplasm is made, but the total enlargement is primarily 

 the result of the entrance of water into the cell under the conditions of 

 imbibition and osmosis. The enlargement of the cell depends, therefore, 



