85 



quantity. 



The Darlington and Coleman four-week climatic avera.^-es 

 and the plant graphs correlate well, probably for the reason 

 given in -^he ciBe of Baltimore. For Darlington, temperature 

 index value remains praotioally constant for the first three 

 periods. The graph of dry weight descends from the period 

 beginning May 15 to the period beginning May 50 following 

 a corresponding decrease in sunshin*? intensity but the slope 

 of the plant graph is not steep probably since evaporation rate 

 is decreased at the same time. From the period beginning 

 May 50 to the period beginning June 13 dry weight production 

 rises a little although sunshine intensity falls again. We 

 may suppose this to be relate! to the fact that the rate of 

 evaporation also decreases thus counteracting the effect of 

 the decreased light intensity. The period beginning June 26 

 shows very good conditions and the plant graph rises again. 

 The period beginning July 10 also shows very good conditions, 

 high temperature index, high light intensity and low evapora- 

 tion rate and the plant graph rises to an extremely/ high value. 

 It seems impossible to relate the four-week climatic averages 

 for the periods beginning July 10 a .d July 84, or the condi- 

 tions during the second two weeks of these oeriods to the de- 

 crease in the plant growth rate from 'h- first oeriod to the 

 second. Eor the last three periods of the season dry weight 

 decreases wit|i the decreasing temperature index value and sun- 

 shine intensity as would be expected. The graphs for Coleman 

 are quite consistent with the assumptions made in regard to the 

 effect of the three climatic factors. The rate of dry weight 

 production rises as the temper'^tuire index values Increase from 



