1917] Hodgson: Abnormal Water Relations in Citrus Trees 41 



TABLE 1 

 Average Moisture Context 



Average water content 

 in per ■ i 

 Kind of material ( I >i v weight) 



New leaves about two weeks old 242.0 



Full grown leaves of current season's growth 1<;_' .2 



Leaves of one season's growth — about one year old 132.7 



Leaves of two season's growth — about two years old li'fi.l 



Leaves of three or more season 's growth. Over two years 



old 117.6 



Leaves of current season 's growth. Gathered between 



9 a.m. and 12 p.m 164.9 



Same gathered between 1 p.m. and 4 p.m 157.2 



Leaves of current season's growth gathered from behind 



fruits between 9 a.m. and 12 m 166.8 



Same gathered between 1 p.m. and 4 p.m 160.4 



Fruits destined to subsequent abscission, one-third to three- 

 fourths inch in diameter 191.5 



Fruits apparently normal gathered between 9 a.m. and 12 M. 8 260.2 



Same gathered between 1 p.m. and 4 p.m 247.7 



Fruits destined to subsequent abscission gathered between 



9 a.m. and 12 m 201.4 



Same gathered between 1 p.m. and 4 p.m 179.2 



of the fact that as the leaves grow older there is a progressive decrease 

 in water content. 



It is also quite evident that a regular diurnal decrease in the water 

 content of leaves of the current season's growth is manifest during 

 the afternoon. Such leaves averaged 164.9% in water content for the 

 period between 9 a.m. and 12 m. and only 157.2% for the period 

 between 1 p.m. and 4 p.m. This difference does not appear significanl 

 when viewed in the light of the large differences obtained by Living- 

 ston and Brown with some of their material. However, it should 

 be borne in mind that those authors were dealing, for the most part, 

 with much more succulent plants containing a large amount of water 

 storage tissue. Further, it should be noted that these figures are 

 averages, since the determinations on which they are based were not 

 made at the same hours. Individual pairs of determinations fre- 

 quently showed differences of as much as 25% to 30% in as short a 

 period as six hours. On June 5 at 2:30 p.m., with the temperature a1 

 95° F and the relative humidity at 19%, the water contenl of leaves 

 of the current season's growth was 144.3%. At 4 a.m. the nexl morn- 



s The fruits used for these determinations averaged ;> little larger than 

 those gathered in the forenoon and therefore would normally 1><- BOmewhat 



higher in water content. 



