igoo-i.J Effects of Water on Foliage Leaves. 255 



These experiments are difficult to conduct, and several had to be 

 discarded owing to defects in the leav^es and to the entrance of air when 

 filling the apparatus. It was thought that a living leaf would act, in a 

 measure, just as a paper would in the same position, but it was found 

 that there was no important point in common between them. The loss 

 of water from the jar, over which the paper was placed, was uniform and 

 constant, this being shown by the movement of water along the 

 horizontal tube. The number in the column under "distance" indicates 

 a distance from the fixed point placed out towards the open end of the 

 tube, so that the larger number indicates a diminished volume of liquid 

 in the apparatus, and the smaller number an increased volume. The 

 diameter of the tube was such that 10 cm. in length indicated i cub. 

 cm. of water. 



From these experiments we may conclude that the leaves used, 

 absorbed water, as vapour from the air, and as liquid from the tank. 

 There was generally a loss of water from the tank during the night and 

 a gain during the day. The increase in amount in the tank during the 

 day was much greater when the lower side of the leaf was exposed to 

 the air. 



In regard to changes occurring at night, there seemed to be little 

 difference, whether the leaves had their upper side up, or their lower 

 side up. During the day, however, there was a remarkable differ- 

 ence. 



The table showing the relative numbers of stomata is given, though 

 no application is made of it further than to show that the stomata are 

 found upon the lower surface only. 



Filter paper, placed in the position of the leaf in the experiment, 

 produced a steady decrease in amount of water in the tank. 



The question of water absorption by attached leaves is not so easily 

 dealt with. In an experiment with willow twigs it is shown that water, 

 as well as a nutrient solution, may be absorbed by developing leaves. 

 (See exper. Chapter X.). 



Some plants, e.g., Ampelopsis, (Fig. 11), have certain peculiarities of 

 leaf structure which seem to indicate an adaptation for absorption. 

 Such are the corrugations over the veins and in the regions of the 

 stomata. It ma\- be that the striations around the bases of the 



