NOTES AND LITERATURE 



SUNSPOTS, CLIMATIC FACTORS AND PLANT 

 ACTIVITIES 



Variations in solar radiation, if of sufficient magnitude, should 

 be followed by variations in terrestrial climatic conditions. In 

 the absence of long series of determinations of the heat radiated 

 by the sun, meteorologists have turned to variation in the num- 

 ber of sunspots as a possible factor underlying variation in the 

 climatic factors. This involves the assumption that a period of 

 many sunspots ditfers from a period of few spots in heat and 

 light radiation. 



If such climatic factors as heat and precipitation be closely re- 

 lated to the number of sunspots, the number of sunspots should 

 be a factor of importance in determining plant activities. In 

 recent years attempts have been made to correlate growth, espe- 

 cially that recorded in the annual rings of trees, with number 

 of sunspots.^ 



Since any attempt to relate growth phenomena to sunspot 

 number presupposes relationships between climate and sunspot 

 frequency, the botanist should be interested in the attempts of 

 the meteorologist to ascertain the relationship between solar and 

 terrestrial atmospheric phenomena. The purpose of this review 

 is to call attention to certain reeent discussions of this subject. 

 For a review of earlier literature, the reader must refer to 

 Hann's "Handbook of Climatology" and to the careful discus- 

 sion from the biological side in Chapter XIX of Huntington's 

 "Climatic Factor. "^^ 



Heretofore, those w^ho have discussed the interdependence of 

 terrestrial and solar phenomena have been content to plot curves 

 for the two phenomena and to determine the existence of relation- 

 ship between them by similar trends in the two curves. 



The sources of error in such a method are very great. Fur- 

 thermore, it gives no quantitative measure of intensity of rela- 

 tionship. Such a measure can only be secured by means of some 

 correlation or contingency coefficient. 



1 Douglas, A. E., "A Method of Estimating Rainfall by the Growth of 

 Trees." In Ellsworth Huntington's "The Qimatic Factor," pp. 101-121. 



2 Huntington, E., "The Climatic Factor as Illustrated in Arid America," 

 Pub. Carn. Inst. Wash., 192, 1914. 



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