96 OSCILLATIONS OR VIBRATIONS 



creation. For the same reason growth will be more rapid when 

 the sun shines, especially after rain, than when the sky is 

 clouded. 



Some of the distinguished microscopists and physiologists of 

 Germany think that these daily pulsations of growth have also 

 left their mark in the interior of the tree, and that the fine 

 layers in the thick walls of the wood and bast tissues, and of 

 the starch granules, are connected with these daily fluctuations 

 in the growth of plants. " Starch granules are the most easily 

 observed in the cells of the potato, where they are very large. 

 The mode of their formation is indicated by the peculiar mark- 

 ings on their outer surface, each grain having a spot at one end 

 which is called the hilum, or ostiole, with fine concentric lines 

 drawn round it."* 



Grains of starch from the potato. 



The Life Wave. This is that grand vibration of growth 

 which extends through the whole period of the life of the tree, 

 and which carries along with it all the smaller fluctuations of 

 each day and each year. "We have shown that the growth of 

 the different parts of a tree depends on the amount of leaf sur- 

 face put forth by each part into the atmosphere. But there is 

 a continually increasing number of leaves developed during the 

 first period of the life of a tree, and consequently an accelera- 

 tion of growth, not only of each individual part, but of the 

 entire tree itself in the same ratio, until the tree puts forth its 

 maximum amount of foliage, when the wave of growth culmi- 

 nates. The tree has now obtained its greatest elevation and its 

 widest spread. Thus, precisely the same accelerated and gra- 

 dually retarded growth which is manifested by the unbranched 

 first year's shoot, pervades the entire fabric of the tree. The 



* See the author's work entitled " The Plant : an Illustration of the Organic 

 Life of the Animal." 



