98 HOW CROPS FEED, 
is absorbed and decomposed, and a nearly equal volume 
of oxygen is set free,—consists in the simultaneous deox- 
idation of carbonic acid and of-watcr, whereby the former 
is reduced to carbonic oxide with loss of half its oxygen, 
and the latter to hydrogen with loss of all its oxygen, viz.: 
Carbonic Carbonic | Hydro- Oxy- 
gaa OO os Gen. ‘a a. 
co, + HO = co + H, + O, 
In this reaction the oxygen set free is identical in bulk 
with the carbonic acid involved, and the residue retained 
in the plant, COH,, multiplied by 12, would give 12 
maolecules of carbonic oxide and 24 atoms of hydrogen, 
which, chemically united, might constitute either glucos. 
or leyulose, C,, H,, O,,, from which by elimination of 
H,O would result cane sugar and Arabic acid, while sepa- 
ration of 2H,O would give cellulose and the other mem- 
bers of its group. 
Whether the real chemical process be this or a different 
and more complicated one is at present 1 matter of vague 
probability. It is, notwithstanding, evident that this re- 
action expresses one of the principal results of the assim- 
ilation of Carbon and Hydrogen in the foliage of plants, 
§ 12. 
The following Tabular View may usefully serve the 
reader as a recapitulation of the chapter now finished. 
TABULAR VIEW OF THE RELATIONS OF THE ATMOSPHERIC 
INGREDIENTS TO THE LIFE OF PLANTS. 
Oxyagn, by roots, flowers, ripening fruit, and by all 
growing parts. 
CarzBonic AcID, by foliage and green parts, but only in 
the light. 
Absorbed J AMMONIA, as carbonate, by foliage, probably at all times. 
by Plants. | Water, as liquid, through the roots. 
Nitrous AciD aes to ammonia, and dissolved in wa- 
Nitric Acip ter through the roots. 
OzonE 
( MarsH Gas 
} uncertain, 
