40 



CLIMATIC CYCLES AND TREE-GROWTH. 



OLD EUROPEAN TREES. 



It is of course most desirable to carry the tree-records back as far as 

 possible for verification of any feature observed in recent years and for 

 additional information. But one is met by the rapidly diminishing 

 number of specimens and the liability of obtaining records which are 

 not representative of the regions on account of the increasing effect of 

 individual and accidental variations. It is true that in the very homo- 

 geneous region about Flagstaff, Arizona, an average of 5 trees and even 

 of 2 gave a valuable record corroborated by comparisons with larger 

 numbers; but in these European groups the oldest trees are all from 

 the Scandinavian peninsula, and probably the individual trees of 

 which I have samples are representative of widely different localities 

 in a rugged and mountainous country. Even though not homogeneous, 

 the 15 oldest trees have been segregated in 2 groups covering the inter- 

 val from 1740 to 1835. 



Group A represents the inner coast of Norway and includes the 

 following trees: No. B 3, 6s, south of Bergen; No. B 11, Sopteland, 

 south of Bergen; No. B 12, Sogne Fjord; No. B 15, Hardanger Fjord; 

 No. B 16, Sogne Fjord; No. N 2, latitude 68 45'. 



1750. 



1800 



FIG. 10. Growth of old European trees. A, six Norwegian trees, mostly from 

 inner fjords. B, eight trees from Dalarne, Sweden. 



Group B is made up of 8 trees from Dalarne, central Sweden, and 

 1 from Lapland, latitude 64 30'. This group, therefore, represents 

 somewhat more homogeneous conditions, but yet it can not be well 

 summarized in its larger fluctuations. When plotted with Group A, 

 as in figure 10, it shows the latter to have a considerable tendency to 

 reversal, a characteristic already observed in this region. But there 

 are discrepancies in Group B consisting of sudden depressions in growth 



