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



It is at once obvious, looking at the stations, whicii arc in every 

 way comparable, that the critical period in 1917 was considerably more 

 severe than in 1916 (fig. 6), which difference has been pointed out with 

 respect to the yield of the Edison orchard. It is also equally evident 

 that the water los.s from the soil and plants has a most profound effect 

 in ameliorating the atmospheric evaporating power and that this effect 

 is cumulative with the direction ofi the prevailing winds. Thus at 

 Edison the "Desert" atmometer lost an average of 69.1 ec. to 48.1 ee. 

 lost by the "Grove" station and at East Bakersfield the .same stations 

 lost water in the ratio of 94.0 ec. to 71.7 cc. At Edison the orchard 

 environment during 1916 was sufficient to cut down the asperity 

 of the climate about 45 per cent, while at the Kellogg place in 

 1917 it was sufficient to reduce it 31 per cent. The atmometer 

 inside the tree lost only two-thirds of that lost by the instrument at 

 "Grove" station or only 45 per cent of that at the "Desert" station. 

 Thus we can see the marked effect of an orchard in modifying its 

 own environmental complex. It is undoubtedy this influence which 

 the orchard manifests per se which explains to some degree why it is 

 that as orchards planted in exposed districts grow older, the percentage 

 of yield increases more than the increase in size of tree. The fact that 

 inside fruit is subjected to an entirely different climate than exposed 

 fruit serves to explain why it is notably of better texture and grade 

 and why it possesses so few large and protuberant navels. We have 

 observed that Navel oranges grown in the University of California 

 greenhouses are of markedly superior texture and navel conformation 

 to those produced outside, where conditions are not so mild or uniform. 

 Again, it is this cumulative modification of the climatic complex fol- 

 lowing the direction of the prevailing wind which explains the fact 

 that a notably heavier set of fruit occurs on the .south and east side 

 of the trees. This condition has been frequentlj' mentioned and was 

 quite marked at Edison in 1017. 



But the most striking modifications in climatic conditions are to be 

 seen with reference to the situation at East Bakersfield. Although the 

 Desert station atmometer lost an average of 94.0 cc. the Alfalfa station 

 instrument lost only 18.5 cc. or only 20 per cent as much. Reference 

 to table 5 serves to show that here is a climatic change within a 

 half mile in the San Joaquin desert of the same magnitude as that 

 between Miami, Florida, and Tucson, Arizona. The effect is, of course, 

 largely due to the fact that the alfalfa transpires at a tremendous rate 

 and the atmometer cup at that station was continuously bathed in an 



