Qg2 BOTANICAL GAZETTE [FEBRUARY 
The transpiration was estimated in each case by comparison with 
the transpiration of the control plants, the transpiration controls 
being also represented as 100. By joining these points, a curve was 
obtained representing the rise and fall of the transpiration in com- 
parison with the somewhat steady rise of the green weight in these 
selected cases. In all charts green weight is represented by the con- 
tinuous line and transpiration by the broken line. 
In selecting these figures, care was taken to omit all in which the 
results might appear to be large on account of very small growth in 
Fic. 4.—Correlative growth and transpiration in soils to which NaNO, was added. 
the control. Had such been included the results would have been even 
more striking than they stand. 
An inspection of fig. 3 shows that potassium sulfate in particular 
acts as an economizing factor (agent) in transpiration. In this case 
the curve representing the transpiration of the plants lies entirely 
beneath the green weight curve. The transpiration curve rises as the 
green weight curve rises but the rise is not exactly parallel. This 
fact harmonizes with the relation brought out in a preceding para- 
graph dealing with the relative quantities of water required where the 
corresponding increase in green weight was small and where it was 
