AGE OF CONIFEROUS TEEES. 15 



arrested till the death of the individual and the subsequent de- 

 composition of its tissues is complete. 



A cross section of the trunk of a large coniferous tree shows that 

 the annual rings nearest the central pith are the broadest, and that their 

 width diminishes as they recede from the centre to the bark.* The 

 diminution is not symmetrical, a ring of a certain width in any part 

 of the section is not precisely so much narrower than the one within 

 it, or so much broader than the one immediately without it. On the 

 contrary, the irregularity in this respect is very considerable, so that a 

 ring is often found which is broader than one nearer the centre, t This 

 irregularity is believed to be due to climatal changes. During a long 

 and warm summer a Coniferous tree will make much more growth than 

 during a wet and comparatively cold one, and it is not improbable that 

 the fluctuations in the seasons are represented by the different widths of 

 the rings. The general principle is, however, never departed from; the 

 rings more remote from the centre diminish in width as they approach 

 the bark. In very aged trees the rings near the outside are so close 

 together that they can only be counted with difficulty, upwards of one 

 hundred of them scarcely occupying a breadth of more than from one 

 to two inches. 



The age attained by Coniferous trees varies very much in the 

 different families. Some members of the Cypress tribe complete their 

 evolution in a few years; the gigantic Sequoias of California have 

 been living during the greater part of the time that separates us from 

 the commencement of the Christian Era. Between these extreme cases 

 are numerous examples of greater or less longevity; thus the Yew is 

 known to live over a thousand years, while the American Balsam Fir 

 rarely attains the " appointed age of man." 



The following estimate, given by various authorities, of the ages 

 attained by some of the largest Coniferous trees must be accepted only 

 with a degree of reservation corresponding to the difficulty experienced 

 in ascertaining anything like an approximation to the truth. 



The Calif ornian Big Tree (Wellingtonia 



gigantea) 

 The Ked "Wood (Sequoia seinpervirens) 

 The Yew (Taxus toccata) . 

 Deciduous Cypress (Taxodium distichum) 

 Himalayan Cedar (Cedrus Deodar a) 

 Cedar of Lebanon (Cedrus IAbani) 

 Douglas Fir (Abies Dbwjlasii) 



from 1,500 to 2,000 years. 



1,300 „ 1,750 „ 



1,100 „ 1,250 „ 



750 „ 1,000 v 



750 „ 900 „ 



600 „ 800 „ 



450 „ 600 „ 



* The cross section of a large Wellingtonia felled in California for the purpose of ascer- 

 taining its a^e, showed the width of one hundred rings nearest the centre to bo 13 inches, 

 and that of one hundred rings nearest the bark to be 3 inches only. 



+ "The separate annual rings are not always of uniform thickness, but are often more 

 strongly developed on one side than the other. "— Thomas Structural Botany, p. 365, 



