Mak. 1903.] BOTANICAL SOCIETY OF EDINBUEGH 407 



rings, seems to have completed the argument in favour of 

 the theory. For since then the controversy has ceased. 

 But the theory is so contrary to what is known of life 

 that gradually it is beginning to be doubted, and now 

 distinguished professors of forestry hesitate to commit 

 themselves either for or against it. 



We will quote Dr. Asa Gray's explanation of the 

 theory •} " For the tree (unlike the animal) is gradually 

 developed by the successive addition of new parts. It 

 annually renews not only its buds and leaves, but its wood 

 and its roots, everything, indeed, that is concerned in its 

 life and growth. Thus, like the fabled ^Eson, being 

 restored from the decrepitude of age to the bloom of 

 youth, the most recent branchlets being placed by means 

 of the latest layer of wood in favourable communication 

 with the newly formed roots, and these extending at a 

 corresponding rate into fresh soil, why has not the tree 

 all the conditions of existence in the thousandth that it 

 possessed in the hundredth or the tenth year of its age ? 



" The old and central part of the trunk may, indeed, 

 decay, but this is of little moment so long as new layers 

 are regularly formed at the circumference. The tree 

 survives, and it is difficult to show that it is liable to 

 death from old age, in any proper sense of the term." 



It is clear De Candolle sincerely believed in his theory, 

 for he worked continuously a number of years gathering 

 evidence in its favour. The literature dealing with notable 

 trees was at his command. This, along with his own 

 observations, led him to believe that the oaks were among 

 the veterans of Europe, but that of all species the yews 

 attained the greatest age (of course it will be remembered 

 he arrived at this judgment before the Sequoias or the 

 Big-trees of California were discovered). From a number 

 of sections of trees of various species, he assumed that he 

 could determine an average growth by measuring the 

 annual increment of each species. Thus he made the 

 increase of the oak and yew on an average to be one- 

 twelfth inch in diameter annually. And with tliis rate of 

 increase, he computed the ages of three celebrated yews in 



* Page 80, vol. 2, of " Gray's Essays," published by Macniillan & Co., 

 London, 1889. 



