THE NITRIC AvID OF THE ‘SOIL. Q71 
Nitric Acid as Food to Plants.—Experiments demon- 
one that nitric acid is capa of perfectly supplying 
f vegetation with 
nitrogen were 
first made by 
Boussingault 
(Agronomic, 
Chimie Agri- 
cole, ete., 1, 210). 
We give an ac- 
jm count of some 
of these. 
Two secds of 
adwarfSunflow- 
er (Helianthus 
N 
5 argophyllus), 
‘ 
were planted in 
each of three 
pots, the soil of 
which, consist- 
ing of a mixture 
of brick - dust 
and sand, as well 
as the pots them- 
selves, had been 
thoroughly 
freed from all ni- 
trogenous com- 
pounds by igni- 
tion and wash- 
ing with distill- 
Fig. 9. ed water. To 
the soil of the pot A, fig. 9, nothing was added save the 
two seeds, and distilled water, with which all the plants 
were watered from time to time. With the soil of pot 
C, were incorporated small quantities of phosphate of lime, 
oo i l 
