COLOR 179 



ed into heat is demonstrated b^^ the following 

 ingenious experiment designed by Kny. 

 Three similar glass vessels with parallel walls 

 are filled with distilled water. In one vessel 

 a number of green leaves of canna are placed, 

 and in another such number as to offer the 

 same amount of surface as those in the first, 

 but which contain a large amount of antho- 

 cyan. The third vessel is left unchanged, and 

 all are placed in sunlight of equal intensity. 

 A certain rise in temperature naturallv ensues 

 in the water in the third vessel ; a greater rise 

 occurs in the first, showing that chlorophyll 

 converts a portion of the light into heat, 

 while the greatest increase takes place in the 

 second, where, in addition to the action of 

 the chlorophyll, the converting power of the 

 anthocyan is exerted. The difference between 

 the temperature of the vessels containing the 

 green and red leaves often amounts to 4° C, 

 which is due entirely to the action of the 

 anthocyan. 



The "screen theory" supposes that the chief 

 purpose of anthocyan is to protect chlorophj^U y, 

 and other nitrogenous and unstable sub- theory 

 stances in transit and in situ from being 

 broken down by the too intense action of 

 light rays. A second theory holds that the 

 development of heat and energy from a layer 

 of anthocyan is an aid to the translocation 



screen 



