39 

 synthesis taking place, '^specially at the yellow hand. Heat is 

 also most developed at this end while light is "best developed at 

 the violet end. Hence green is an intermediate color it raa^^ he 

 the color of chlor. since it ahsorhs the other rays such as the 

 red and hlue. Cyanophyceae — hlue-green Algae — live "best in warm 

 atmospheres. 



Similf icance of Reds . 

 Sometimes green does not develop a great enough amount of heat, 

 so red leaves may he developed in the spring. Stahl and King 

 have experimented on red leaves of maple and beech. Greater hea^t ' 

 given off by red leaves. Hence it 1ms been thoiiglit that the red 

 of leaves is developed. Often on the lovirer side of shade leaves 

 and water leaves for the conservation of heat. Many plants which 

 live over winter as mints have red color on lower surface. 



Autumn Coloration . 

 Caused by- Introdxxction of new substance. Anthreyan, if acid it Its 



, if not acid . This substance is a resi^lt of 



breaking up of the chlorophyll. Kerner considers the leaf Gontim^es 

 to do its work, a short time after the red color is foiind. 



Objections to Kerner 's theory. 



1. It appears to contradict itself. 



2. Amount of temperature change, very small. 



Observational Objects. 



1. Spring leaves generally red. 



2. Leaves may turn red whenever their work is done. 



