ATMOSPHERIC AIR AS THE FOOD OF PLANTS. 57 
air-tight, upon a glass plate,and having two glass tubes 
cemented into its neck above, as in fig. 6. Through 
an aperture in the centre of the glass plate the stem of 
the plant experimented on was introduced, so that its fo- 
_liage should occupy the bell, while the roots were situated 
in a pot of earth beneath. Two young bean-plants, grow- 
ing in river sand, were arranged, each in a separate appa- 
ratus, as in the figure, on June 19th, 1859, their stems be- 
ing cemented tightly into the opening below, and through 
the tubes the foliage of each plant received daily the same 
quantities of moist atmospheric air mixed with 4-5 per 
cent of carbonic acid. One plant was supplied in addition 
with a quantity of carbonate of ammonia, which was in- 
troduced by causing the air that was forced into the bell 
to stream through a dilute solution of this salt. Both 
pants grew well, until the experiment was terminated, on 
the 11th of August, when it was found that the plant 
whose foliage was not supplied with carbonate of ammo- 
nia weighed, dry, 4.14 gm., while the other, which was 
supplied with the vapor of this salt, weighed, dry, 6.74 
gms. The first plant had 20 full-sized leaves and 2 side 
shoots; the second had 40 leaves and 7 shoots, besides a 
much larger mass of roots. The first contained 0.106 
em. of nitrogen; the second, double that amount, 0.208 
gm. Other trials on various plants failed from the diffi- 
culty of making them grow in the needful circumstances. 
The absorption of ammonia by foliage does not appear, 
like that of carbonic acid, to depend upon the action of 
sunlight; but, as Mulder has remarked,* may go on at 
all times, especially since the juices of plants are very fre- 
quently more or less charged with acids which directly 
unite chemically with ammonia. 
When absorbed, ammonia is chiefly applied by agricul- 
* Chemie der Ackerkrume, Vol. 2, p. 211. 
3* 
