July ;i9a0.] 



OGURA:— GROWTH IN THICKNESS. 



99 



same relation, which differed from the above stated observations of 

 other authors. 



G. Growth and climate 



The growth of trees is obviously controlled by external influence, 

 especially by meteorological changes. Among the meteorological 

 changes, the precipitation amount is the most changeable factor and 

 there are several records on the correlation between growth and 

 precipitation, e. g. Mischke 1 on fir, Jost 2 on many angiospermous 

 trees, Steward on oak, and especially Douglass 3, 4 on Big-tree. 

 I examined eight samples of disks from different trees from 

 Nikko, and compared with the meteorological records of Ashio, ten 

 miles away from there, and found that there was no remarkable 

 coincidence between growth and precipitation, except three cases, one 

 of which (1916, Taisho VI) showing better growth and abundant 

 precipitation, while two other cases (1910, Meiji XLIII ; 1902, Meiji 

 XXXV) showing worse growth when the amount of precipitation 

 was very abundant. Though the former case is in accord with the 

 results of man}' authors, in the latter the relation is reversed. The 

 latter condition may be ascribed to the excessive amount of precipita- 

 tion and to the unusual changes of climate, which was the cause of 

 bad harvest in these two years. 



Though there are meteorological changes daily as well as yearly, 

 it is not certain whether there is a periodic cycle in a certain number 

 of years. Recently it has been reported by several authors, that 

 there is a certain correlation between climate and number of sun-spots. 

 Douglass 3 found in Arizona a remarkable agreement of growth and 

 precipitation, the latter also agreeing with the increase of number of 

 sun-spots. Afterward, he 4 found the same relation in trees in Europe. 

 Nevertheless, my observation on Japanese trees are not in accordance 

 with them. 



1. Mischke, K. (1890) Beobachtungen iiber das Dickenwacksthuni der Conifer- 

 en.— Bot. Centrb., Bd. 44. 



2. Jost, L. (1892; Beobachtungen iiber den zeitlicben Verlauch des secundaren 

 Dickenwachsthums der Bauine. — Ber. Deut. Bot. Ges., Bd. 10. 



3. Huntington, E., Douglass, A. E., etc. — loc. cit. 



4. Douglass, A. E. (1917) Climatic records in the trunks of trees. — Amer. 

 Forest., vol. 23. 



