so 



five periods of the growing season are as in the Oakland cul- 

 tures approximately inversely proportional to the evaporation 

 for th° last two weeks of eaoh of the four-week periods, fhis 

 may be seen by comparing the slope ii recti on of the dry weight 

 graph for the interval from the period beginning May 19 to the 

 period beginning July 14 with the slope airection of the two - 

 week evaporation graph from the period beginning June 2 to 

 the period beginning July 28. The rise in the dry weight 

 graph from the period beginning June 30 to the period beginning 

 July 14 is not as great as would be expected from the I07; ra-^e 

 of evaporation during the last half of the latter period (see 

 the period beginning July 28 on *he two-week graph). It will 

 be noted from the tv:o-week graph, however, that the values of 

 the temperature index and of sunshine intensity are both low 

 for the two-week period beginning July 28 and this probably 

 explains the depresssicn of the dry weight value for the 

 four-week period beginning July 14. From the last-named per- 

 iod to the end of the season the values of dry weight are rel- 

 atively lower than would be expected from the four-week averages. 

 A possible explanation for ea^h of these low values is to be 

 found, however, In the fact that one or more of the three 

 climatic conditions is unfavorable for growth during the last 

 half of the periods. The low value for the four-week period 

 beginning July 6 may be accounted for by low sunshine inten- 

 sity and high evaporation rate during the last two weeks as 

 shown by the period beginning Aug. 11 on the two-week graph. 

 The last two weeks of the four-week eriod beginning Aug. 11 

 show a very low sunlight intensity value fperiod beginning 

 Aug. 26 on the two-week graph), ^ry weight for the period 



