COLORS OF NORTH AMERICAN FLOWERS 



nitrogen, phosphorus, potassium, magnesium, and iron, than 

 carrotin, which is composed of only carbon and hydrogen. 

 Anything, therefore, which retards or prevents the formation 



Fig. 106. Woodbine. Psedera qiiinquefolia 

 Small green flowers 



of chlorophyll, as the absence of the proper elements, will cause 

 the flower to become yellowish; and, as has been shown, carrotin 

 is much more persistent in intense sunlight than the green 

 pigments. In the beginning of entomophily (adaptation to 

 insects) there would naturally be from time to time more or 



231 



