1917] Hodgson: Abnormal Water Relations in Citrus Trees 49 



this water is utilized by the leaves. Indeed, almost exact quantitative 

 results were obtained, the percentage of water loss of the fruit being 

 approximately equal to that gained by the leaves. (See Experiment 

 2.) Dye stuff experiments have shown that there exist no physical 

 difficulties for such procedure. It then remained to determine whether 

 this phenomenon actually occurred in fruits on the tree. For this pur- 

 pose the procedure of the previous experiments was used, namely, 

 moisture determinations and water transport studies by means of dye 

 stuff solutions. However, the evidence here is not so conclusive, as 

 all the experimental work was necessarily performed on shoots in 

 situ, which introduces a number of uncontrollable adventitious vari- 

 ables, as has been well pointed out by Dixon 10 in his criticism of trans- 

 piration measurements performed on shoots detached from the tree. 

 The influence of the remainder of the tree is admittedly an unknown 

 quantity. Nevertheless it is believed that the data obtained are 

 strongly indicative of conditions as they exist. 



From table 1 it will be seen that there exists a considerable differ- 

 ence in water content between those fruits, destined to remain and 

 mature when picked before and after noon. Fruits of this sort 

 gathered in the morning averaged 12.5% more water than those 

 gathered in the afternoon. As is mentioned in the footnote to table 1 

 this difference is probably considerably smaller than it should be on 

 account of the larger size of the fruits used in the afternoon determin- 

 ations. That this same condition obtains in those fruits destined to 

 subsequent abscission is also shown in table 1. In this case the difffer- 

 ence is 22.2%. There are several ways in which a decrease of water 

 content in the fruit can be explained : ( 1 ) the water is actually 

 drawn back from the fruits by the leaves; (2) the normal supply to 

 the fruits is considerably reduced by being appropriated by the leaves 

 before it reaches the fruits ; or ( 3 ) the transpiration ratio of the fruit 

 to the leaves is markedly increased. If the fruit possessed no stomata 

 and did not transpire, the first condition must hold. However, the 

 fruit does possess stomata in some numbers and is actively transpiring 

 at the same time as the leaves. Therefore it seemed advisable to make 

 a cursory comparative study of the number of stomata per unit of 

 area on the fruits and leaves and also of the ratio of transpiring area 

 of the fruits and leaves situated immediately behind them. While 

 the young fruit possesses stomata even before the style is exfoliated, 

 stomatal counts showed that the number is comparatively small, rang- 



10 Transpiration and the ascent of sap in plants (London, MacMillan, 1914) 

 pp. 120-125 



