GROWTH. 79 



EXPERIMENT 102. 



FREEZING OF PEA, BEAN, AND WHEAT. 



Place some air-dry seeds of the Pea, Bean, or Wheat for several 

 hours in a temperature of 5 to 10 degrees below zero centigrade. 

 They do not lose the power of germination, as may be shown. The 

 same kinds of seeds when saturated with water are killed by this 

 temperature, and are unable to germinate. 



Remark. Trees behave similarly. In winter, when they contain but 

 little water, they endure a high degree of cold ; a late spring frost kills 

 them, because the trunks and twigs are full of sap. 



EXPERIMENT 103. 



EFFECT OF HIGH TEMPERATURE ON SATURATED SEEDS. 



Place 30 swollen seeds of Peas or Wheat for a quarter of an 

 hour in water at a temperature of 60 to 70 C., and then place in 

 a germinator. They do not germinate, while 30 other seeds placed 

 in the germinator after soaking develop normally. 



62. Protoplasm which has been killed by low or high tem- 

 perature undergoes molecular changes ; it then becomes per- 

 meable to acids and coloring matters. (See 60.) 



EXPERIMENT 104. 



ESCAPE OF CELL-SAP OF BEET KILLED BY LOW TEMPERATURE. 



Frozen and unfrozen pieces of Beet are placed in water ; the 

 first colors the water red, the latter does not. The protoplasm of 

 the frozen cells allows the colored sap to pass through it. 



EXPERIMENT 105. 



ESCAPE OF SAP FROM A BEET KILLED BY HIGH TEMPERATURE. 



Perform the above experiment, using pieces of Beet, one of which 

 has been in water at a temperature of 60 to 70 C. The result is 

 the same as in Experiment 104. 



EXPERIMENT 106. 



ESCAPE OF CELL-SAP CONTAINING OXALIC ACID FROM A STEM OF BEGONIA. 

 KILLED BY HIGH TEMPERATURE. 



Place two pieces of a petiole of Begonia in distilled water after 

 one of them has been treated with water at a temperature of 60 to 

 70 C. until colorless. Add a solution of calcium chloride to the 

 dishes containing the pieces. The water in one dish remains clear, 



