AGE OF SINGLE TREES. 73 



estimated within 10 or 20 years, 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. Detekminatiox by the Number of Anntal 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. Deteumixatiox 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 



eccentric. 



I. Felled Trees. 



It is by far the best method to count the concentric rings on 

 a stump, and, if necessary, fell a tree for the purpose. 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 tree (Hornbeam, Alder). In the case 

 of suppressed trees, the true rings are frequently so narrow, 

 either all round or in parts, that they are difficult to distinguish. 



