NOTES AND COMMENT 



The cultivation of the Washington navel orange has gradually been 

 extended in southern California from the humid coastal regions to 

 some of the arid interior valleys, where the yield is greatly reduced 

 by the premature fall of young fruits. J. E. Coit and R. W. Hodgson 

 have recently investigated the cause of the "June drop" of young 

 oranges (Univ. Cal. Pubns. in Agrl. Sci., vol. 3, no. 11), establishing 

 the fact that the arid conditions of such localities as the southern 

 San Joaquin Valley are directly responsible for the drop. Evidence 

 is given to show that high rates of transpiration cause such a reduc- 

 tion in the water content of the tissues that the formation of a definite 

 abscission layer takes place in the stems of the young fruits. Ameliora- 

 tion of the local atmospheric conditions by the growing of irrigated 

 crops near by has been found to reduce the loss in the oranges. By a 

 comparison of local evaporation rates with those of the great conti- 

 nental areas it is shown that an irrigated crop growing in the proximity 

 of an orange grove serves to reduce the evaporation from a rate like 

 that of Tucson, Arizona, to one near that of Miami, Florida. 



The climatic maps of the United States, or of individual states, show 

 such widely separated and gracefully sweeping isoclimatic lines that we 

 are prone to overlook the very considerable differences of climate that 

 may exist within very small areas. These differences may well be of 

 great agricultural importance even in less diversified states than 

 ( 'alifornia. 



An interesting paper has been contributed to the January-March 

 issue of the American Fern Journal by Mr. Ellsworth P. Killip, de- 

 scribing the fern flora of Panama. The lowland jungles of the Canal 

 Zone were visited and also the summit of the Sierra Chiriqui, which 

 forms the continental divide north of the isthmus. Both localities were 

 found to have a rich and varied representation of ferns. 



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