318 University of California Publications in Agricultural Sciences [Vol. 3 



almost saturated atmosphere. The windbreak served to prevent the 

 blanket of moist air from being rapidly dissipated. The loss from 

 Tree staticm is seen to be 35.8 cc, or only 30 per cent of that lost by 

 the Desert instrument. Although the effect of the alfalfa cannot be 

 exerted at any very considerable height above the ground, still it is 

 certain that the orange trees (with the young developing fruits') sur- 

 rounded by this transpiring alfalfa are literally bathed in a damp 

 atmosphere; at any rate so far as the tree is concerned it is subjected 

 to a very different climate from that which obtains on the desert. The 

 influence of the alfalfa in modifj'ing the atmospheric humidity can 

 clearly be seen when the crop of oranges is picked, for under these 

 conditions most of the fruit is borne near the ground and less in the 

 tops of the trees. At Tree station. East Bakersfield, thermo-hygro- 

 graph readings were taken for a period of twenty days. A study of 

 the record for the period of the investigation shows some interesting 

 results. At no time did the temperature rise above 107° F although 

 in the laboratory, a quarter of a mile away, temperatures of 110° to 

 112° F were registered several times. The most significant feature, 

 however, is the relative humidity curve. The lowest humidity reached 

 was 25 per cent, wliich occurred at the time that the 107° F tempera- 

 tures were recorded, July 9 and 21. The average relative humidity 

 during the day was between 40 and 50 per cent. In 1916 at Edison 

 we recorded humidities as low as 10 per cent and the average relative 

 humidity was between 25 and 35 per cent. It is unfortunate that we 

 were not able to obtain simultaneous temperature and humidity read- 

 ings at the Desert station in 1917, but in view of the fact that the 

 1917 season has been shown to be much more severe than the 1916 

 season there is little doiibt that in 1917 the relative humidity was 

 somewhat lower and the temperature somewhat higher than in the 

 former season. 



"We recognize clearly that in agricultural enterprises it is unsafe 

 to rely upon climatic averages. It is well known that with some crops 

 suece.ss or failure depends largely upon the extremes of climatic con- 

 ditions experienced during a certain critical period in their growth. 

 However, it should be borne in mind that conditions which tend to 

 ameliorate the environmental complex not only raise the general 

 average favorably, but also have a distinct modifying effect upon 

 extremes in weatlier conditions which may occur. Indeed, it seems 

 probable that this is the most important effect of the alfalfa and 

 windbreaks in the Kellogg orchard. It is not so much the liigher 





