OF GROWTH IN TREES. 93 



grows, the life movements forward are accelerated and then 

 retarded, year after year. These fluctuations of growth in trees 

 may be compared to the rising and the falling of a wave, which 

 attains a certain elevation over the ocean's surface, and then 

 sinks into its depths and disappears. 



Now, the trunk of a tree rises at first from the seed as an 

 herbaceous stem; but, as it usually becomes more or less woody 

 before the close of the vegetative season, when it enters on the 

 stage of rest in Winter, it is not destroyed by the severity of 

 the season. Only its foliage perishes. "We have seen how the 

 foliage is renewed upon fresh shoots from the terminal and lat- 

 eral buds of the young stem every season : in fact, the axis 

 with its branches is the only permanently enduring part of the 

 tree. 



In some trees these fluctuations of growth, or vibratory 

 movements between a state of rest and that of motion, last for 

 hundreds and even thousands of years ; but the tree, like every 

 other living organized form, is compelled at last to pay back 

 the debt due to Nature, and yields to the earth and air those 

 borrowed elements out of which it originated. 



In order that the reader may form a more definite idea of the 

 nature of these waves of growth, we have ventured to classify 

 them as follows. In the life of a tree, we may distinguish three 

 principal waves of growth, or accelerated and retarded vital 

 movements. 



The Annual Wave. During Winter, the trees of temperate 

 climates, like the seeds in the ground, are in a state of passive 

 vitality. Life exists in both although there is no perceptible 

 vital movement ; for there is no chemical decomposition or 

 separation of their parts. Alexander von Humboldt defines 

 the power of life as that inward force which dissolves the fet- 

 ters of the chemical affinities, and prevents the union of the 

 elements or original components of organized bodies. There- 

 fore, there cannot be a more infallible mark of death than cor- 

 ruption. It indicates that the elementary principles or raw 

 material of what was once a plant or an animal, are begin- 

 ning to obey their pristine laws, and to arrange themselves 

 in accordance with their chemical relations to each other. 



