AGE OF TREES. 73 



conditions under which a tree has grown up, its age can be 

 estimated within 10 or 20 years, at any rate as long as height- 

 growth continues. In the case of very old trees the limit of 

 accuracy is much wider. At all times this method requires 

 much practice and experience, and even then it yields only 

 approximately correct results. 



iii. DETERMINATION BY THE NUMBER OP ANNUAL SHOOTS. 



In the case of species which leave clear marks of the 

 successive annual shoots, the age can be ascertained by 

 counting these shoots from the top downwards and by 

 adding a proportionate number of years for the lowest part of 

 the stem, where the marks are no longer distinguishable. 

 This method is, in Europe, only applicable to the various 

 species of pine up to a certain age, less so in the case of firs, 

 and not at all in that of larch or of the ordinary broad-leaved 

 species. 



iv. DETERMINATION BY MEANS OF PRESSLER'S INCREMENT BORER. 

 As explained in Chapter I., with this instrument a narrow 

 cylinder of wood can be extracted from the stem on which the 

 concentric rings may be counted. The instrument does, how- 

 ever, not work satisfactorily beyond a depth of 6 inches, so 

 that the centre can only be reached if the diameter of the tree 

 does not exceed 12 inches. Even then it is frequently difficult 

 to hit off the centre, as the trees grow generally more or less 

 excentric. 



I. Felled Trees. 



It is by far the best method to fell a tree and count the 

 concentric rings on the stump. At the same time this is not 

 always an easy operation, and in some cases it is altogether 

 impracticable. It is easiest in the so-called ring-porey broad- 

 leaved species, and in conifers, which produce a darker coloured 

 summer, or autumn, wood than that formed in spring. 

 Frequently false rings appear. These may be distinguished 

 from true rings by finding that they do not run right round the 



