Leaf Water -content, and Transpiration Rate . 
231 
Fig. 2. Graphs (based on the results given in Table II) showing the lack of agreement between 
relative transpiration and stomatal aperture. s *= stomatal aperture ; E = atmometer loss ; 
T 
- = relative transpiration. 
The discordant results obtained in this series when considered in con- 
junction with the water-content of the transpiring plant — as indicated by 
the difference between the quantity of water transpired and the quantity 
absorbed — constitute confirmatory evidence of the * incipient drying * 
hypothesis of Livingston and Brown (see p. 232 above). In Table I above it 
will be observed that during the experiment the plant transpired 11-87 grm. 
of water and absorbed only 10-57 grm., involving a loss to the plant of 
1-30 grm. It is also significant that the greatest loss, namely 0-45 grm., was 
between 12 noon and 13.30 p.m., from which point onwards the graph of 
relative transpiration falls. From 3.30 p.m. onwards the plant absorbed 
slightly more water than it transpired and the transpiration rate remained 
approximately constant. The conclusion is that the excessive transpiration 
early in the day caused a lowering of the water-content of the transpiring 
cells and a drying out of the walls, this in its turn exerting a check upon 
transpiration (and so a decrease in relative transpiration), before the 
evaporating power of the air began to decrease. 
Consideration of Table II above shows the reverse process in action. 
The total amount of water transpired was 22-43 g rm - an d the amount 
absorbed 23-12 grm., a gain of 0-69 grm. Throughout the experiment the 
rate of absorption never fell appreciably below the rate of transpiration, 
