Wild Flowers as They Grow 



vibrations of heat, and the two together act chemic- 

 ally upon the watery substances in the cells and 

 thus bring about changes of tension, and hence of 

 growth. He points out the Httle known fact that 

 every night the rays of a Daisy grow somewhat, and 

 that it is only while they go on growing that the 

 closing movements continue. Here, too, the cold 

 scientific reason of the pretty crimson petal tips, 

 immortahsed by Bums, comes in, for they are due 

 to a substance known as anthocyanin which has the 

 special property of changing light rays into heat 

 rays. When the Daisy is closed and its sheath 

 folded round it these crimson tips form a dome over 

 the central disk and, consequently, catch the full 

 benefit of the sun's rays directly it appears and thus 

 greatly facilitate the production of the necessary 

 heat. This closing of the bloom is naturally a 

 measure of protection. 



The leaves are broad and flat and are arranged 

 in a circular plate that lies closely upon the ground. 

 Nothing can grow beneath them and they are, 



i6 



