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



As to the ultimate stimulus beyond abnormal water relations we 

 can do little but speculate. Lloyd 50 has expressed the idea that increase 

 in temperature following water deficits may be the ultimate stimulus 

 to abscission. It has long been known that plant parts, when for any 

 reason deprived of a normal supply of water, suffer an increase in 

 internal temperature. In an effort to furnish additional evidence as 

 to the presence of abnormal water relations, as well as to obtain some 

 idea of the temperature changes incident to such water deficits, we 

 took some temperatures of fruits destined to fall, fruits suffering 

 from a water deficit by reason of the fact that the tree was permitted 

 to suffer for lack of irrigation, and temperatures of normal fruits. 

 These are found summarized in tables 9 and 10. It will be seen that 



