Relation of Annual Rings to Age. 

 relation of growth. — Continued. 



171 



Years. 



] 883 



L882 



1881 



1880 



1879 



1878 



1877 



1876 



1875 



1874 



;isr^ 



1872 



Sums. 



Means. 



Rain. 



R. II. 



50.7 



7.24 



20.38 



71.6 



32.8 



4.68 



18.40 



69.1 



42.9 



6.15 



11.95 



69.9 



32.7 



4.65 



15.85 



68.1 



35.5 



5.07 



14.95 



69.9 



18.7 



2.66 



16.40 



69.1 



19.6 



2.79 



11.62 



68.2 



38.3 



5.47 



18.51 



73.0 



52.3 



7.47 



19.77 



73.9 



61.8 



8.83 



14.35 



70.2 



74.7 



10.66 



14.19 





60.0 



8.57 



14.00 





Temp. 0°F 



"1.1 



61.2 



64.2 

 64.3 

 62.0 

 64.6 

 64.5 

 63.0 

 61.8 

 61.5 

 67.0 

 65.0 



In the table on the following page comparison is made with 

 the thickness of rings for each year. The thickness of each 

 ring as given is the mean of the thickness measured in cro^s 

 diameters, and thus of four measurements in each case; and the 

 mean of several rings for the same year, from different trees, should 

 enable us to trace whatever connection there mny be between 

 growth aod meteorological conditions. There is one element here, 

 however, which tends to impair the accuracy of such a comparison, 

 and makes it only indicative. In bringing the same years of growth 

 together, it necessitates comparing the rings of a younger genera- 

 tion of growth with those of an older generation, e. g., the Gen. 

 •Grant Crab No. 1 was eleven years old when cut in 1 883 ; the 

 European Silver Poplar was six years old at the same date, and 

 therefore, in comparing the growth in the two for 1883, the sixth 

 generation of the latter is necessarily brought into comparison with 

 the eleventh generation of the former, and this tends to inac- 

 curacy, since each generation or each ring, does not involve varia- 

 tions dependent upon meteorological conditions alone, but upon 

 ■cycles of physiological change, as will be seen shortly. In our 

 comparisons, therefore, this must be kept clearly in mind and due 

 allowance made. 



^ Measurements in centimeters. Meteorological means for five 

 months, May to Sept., inclusive. 



