96 OSCILLATIONS OE VIBRATIONS 



year's shoot. The reader will be satisfied of this fact by 

 examining the drawing. 



The Daily Wave. — According to Treviranus, the growth 

 of trees is accelerated during the day and retarded in the 

 evening. The principal German physiologists appear to 

 agree as to the fact that there is such a daily acceleration 

 and retardation of growth, though they differ a little as to 

 the precise time of its occurrence. This daily fluctuation 

 is by no means unreasonable ; for growth can only take 

 place through the assimilation of formative materiaj, and 

 this mainly depends on the sun's influence. The vital 

 energies of plants may possibly vary with the degree of 

 the sun's elevation above the horizon, and plants may re- 

 cuperate to some extent during the night, like the animal 

 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 physio- 

 logists 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 markings on 

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



Grains of starch from the potato. 



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

 lines drawn around it."* 



The Life Wave. — This is that grand vibration of growth 



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

 Organic Life of the Animal." 



