Stomata , Leaf Water-content , Wilting of Plants . 375 
had been lost from the leaves. Experiments were therefore carried out to 
determine the change of water-content of the leaves during the preliminary 
acceleration period. The water-content of the cells concerned in transpira- 
tion and stomatal change will depend upon the rate at which water passes 
to these cells from other parts of the plant. Cribbs (6) states that there is 
evidence that a water deficit may be due to the failure of the water- 
translocating system to supply water to the leaves in sufficient quantity to 
counterbalance the loss by evaporation. It appears that he includes in the 
term ‘ translocating system 5 the path of the water through the soil and into 
the roots, as well as the conducting system of the plant. It is self-evident 
that in a dynamic system such as the plant, the water-content of any 
particular region must be dependent upon the rate of water translocation. 
It is evident also that changes in the water-content of the whole plant are 
not necessarily indications of changes in the water-content of any particular 
cell. It is therefore inadvisable to use the former and impossible to use the 
latter for experimental determinations. As a practicable compromise the 
water-content of a single leaf lamina was adopted as a working basis, and 
this was determined in conjunction with measurements of stomatal changes, 
since the latter are easier to obtain and to localize than measurements of 
transpiration rate. In addition, change of transpiration rate is in the 
present instance probably almost wholly dependent upon change of stomatal 
aperture. At the outset, determinations were made of the water-content of 
leaves of all ages from plants of several species, including Eupatorium 
adenophorum > which had been used for many of the foregoing experiments. 
Considerable differences of water-content were found to exist, as indicated 
in Table III, which gives the figures for all the leaves of one shoot. 
Table III. 
Water-content of single leaves of Eupatorium adenophorum. 1 A and 1 B 
are two companion leaves from the same node. The same applies to 
2 A and 2 B, &c. 
Leaf No. 
j B | youngest pa,ir 
2 A 
2 B 
3 A 
3 B 
4 A 
4 B 
5 A 
5 B 
6 A 
6 B 
7 A 
7 B 
% water calculated 
on wet weight. 
81.8 ) 
82*2 i 
85*7 J 
85- 5 1 
86.1 
86- o ( 
85*3 ' 
84-9 \ 
84.1 l 
83- 9 s 
84.9 / 
84- 3! ■ 
8.vS ) 
