igoo-i.] 



Effects of Water on Foliage Leaves. 



253 



Acer, Ainpelopsis, Liriodendron and Tilia were tested, first with the 

 lower surface in contact with the water, and then with the upper surface 

 in contact. It was found that in the case of TiHa it was with the 

 greatest difficulty that leaves free from small holes could be obtained, 

 and that when one was found, apparently without holes, there was 

 observed a very rapid transmission of water through the leaf, and 

 it was necessary to elevate and lower the measuring tube with the 

 greatest care so as to keep the liquid in contact with the leaf and yet to 

 have no pressure against its surface. With the leaf of the Liriodendron 

 the transmission was very slow, and several centimeters pressure did 

 not materially hasten it. During the course of the experiments it was 

 noticed that the humidity of the atmosphere affected the rate of 

 transmission of water. There was a decrease in the rate of transmission 

 of water, associated with a decrease in the humidity of the atmosphere, 

 as indicated by the psychrometer. This was also the case when filter 

 paper was in the position of the leaf, but there was in no instance an 

 increase in volume as resulted with the leaves. 



The records given in the following table show the change in volume 

 of liquid in the apparatus to which the leaf was fixed, the temperature 

 of the room, and the relative humidity of the atmosphere. The 

 measurements upon the horizontal tube of the apparatus are made from 

 a fixed point, so that the figures in the column under "distance" at 

 once indicate an increase or decrease in the volume of liquid in the 

 tank. 



I. III. 



* The larger number denotes decrease, and the smaller increase. 

 t Pressure raised to ten inches for five minutes. 



