96 BOTANICAL GAZETTE [FEBRUARY 
sodium phosphate, rro per cent.; in extracts plus calcium carbonate 
(saturated solution), 163 per cent. of the controls. 
In the former series of experiments there was no comparison 
between the sodium and the potassium salts of the same acid. A 
few comparisons were made in this series of experiments employing 
K,SO, and Na,SO,, the results of which are of some interest, since 
one of the salts functions as a plant nutrient and the other probably 
does not. ‘In the comparison at present under consideration it was 
Fic. 7.—Correlative growth and transpiration in soil extracts to which NaNO; 
was added. 
found that plants grown in soil extracts receiving sodium sulf te 
exhibited a transpiration per unit of green weight equal to 93-9 Ley 
cent. that of the controls, whereas an equivalent amount of potass1um 
sulfate added to extracts of the same soils and in which plants 
were simultaneously grown gave 85.3 per cent. 
A comparison of the effects of two different salts of potassium was 
afforded by the results from the use of potassium chlorid and potas- 
sium sulfate in extracts of the same soil. Sixteen experiments were 
selected in which these two salts had been added to extracts of the 
same soil, and plants grown simultaneously. 
