1910] Coit-Hodgson : Abnormal Shedding of Washington Navel Orange 333 



to result in the inhibition of absorption at the very time of day that 

 water loss by transpiration is greatest. 



13. It has been found possible to modify climatic conditions in an 

 orchard .so as to set crops in every way comparable with those produced 

 in much more climatically favored citrus districts. 



14. Under these modified climatic conditions the abnormal water 

 relations referred to apparently do not occur. 



15. Practical means of amelioration lie in heavier and more fre- 

 quent irrigation, the planting of intercrops, mulching with straw and 

 other materials, protection by means of windbreaks, and a reduction of 

 leaf area by moderate winter pruning. 



16. Measures of an anticipatory nature lie in the judicious selec- 

 tion of the site for the orchard with reference to its exposure, nearness 

 to large irrigated bodies of land, and other features calculated to 

 ameliorate climatic conditions. 



17. Orchardists should be on the lookout for mutant strains which 

 are dry heat resistant and satisfactory in other features. 



This investigation had its inception with the senior author, who 

 began the experimental work in March, 1916. In May, 1916, the junior 

 author became connected with the Division of Citriculture and has been 

 associated in the study of this problem ever since. Early in the in- 

 vestigation it became evident that there were at least two distinct 

 promising lines of inquiry involved in the problem. The first, having 

 to do with the relation of a certain almost ever-present fungus to the 

 falling of the young fruits, is largely the work of the senior author. 

 The second, having to do with the relation of the shedding to environ- 

 mental conditions, although originating with the senior author and 

 receiving constant study by him, constituted the main problem of the 

 junior author, who moreover is responsible for the histological work 

 involved in the investigation. The combination of attack, both on the 

 pathological and physiological side, has given most satisfactory results 

 and it is the belief of the authors that when investigated in a some- 

 what similar manner many of our so-called "physiological diseases" 

 may be better understood. 



The authors wish to ackowledge their indebtedness to Drs. F. E. 

 Lloyd, W. A. Cannon, T. II. Goodspeed, and C. B. Lipman for sugges- 

 tions and assistance, and to Mr. W. W. Worden and Dr. C. W. Kellogg 

 for kindly cooperation in placing their orchard facilities at their 

 disposal. 



Transmitted January 17, 1918. 



