Io6 Forestry Quarterly. 



In the last number of the Quarterly (p. 

 Temperature 576) a paper by Livingston on Plant 

 Coefficients Growth and Climate was reviewed. Now, 



in in collaboration with Mrs. Livingston, he 



Plant has advanced a step — several steps — far- 



Geography ther in consideration of the subject. The 



and authors point out that plant association 



Climatology. boundaries must be considered as peripher- 



ies of certain complexes of environmental 

 conditions. Thus far, investigators of ecological conditions have 

 been unable, successfully, to unravel the tangle of conditions 

 which effect the success of organisms in a given habitat. These 

 environmental factors are water, non-aqueous materials, heat, 

 light and mechanical conditions. What makes the problem of 

 distribution still more complicated is the fact that each separate 

 component of the environmental complex is variable in intensity, 

 in duration and often in quality, as well as variable according to 

 the stage of development of the organism acted upon. The 

 authors in the present paper deal with only one of the environ- 

 mental factors, namely temperature. As is well known, the 

 usual method of dealing with temperatures in their effect upon 

 plant distribution is to add up all the degrees of temperature, 

 above a certain limit, experienced by the plants during the frost- 

 less period. It, however, seemed to the authors that the ap- 

 parent value of temperature summations must rest upon some 

 basic principle of physiology not indicated in the summations 

 themselves. To this end the chemical principle of Van't Hoff 

 and Arrhenius is employed, that is, within certain limits the 

 velocity of most chemical reactions doubles or somewhat more 

 than doubles for each rise in temperature of 10 degrees Centi- 

 grade. This principle has been applied with general corrobora- 

 tion to the functions of plants, since such functions are mostly 

 chemical or at least dependent upon chemical reactions. For 

 example, it has been found, beginning with resting buds, that in 

 the case of the flow^er buds of plum, peach, apple and other fruits, 

 the time required for blooming is reduced by one half for each 

 rise in temperature of 10 degrees Centigrade. If the processes 

 of growth and development do really exhibit temperature coef- 

 ficients, it is plain that the study of environmental temperature 

 factors should deal with these rather than with temperatures di- 



