ELEMENTS OF AGRICULTURE. 
S 
by piants, either through their roots, stems, or leaves 
This last gas, that never enters into the composition of 
the air in a greater degree than a hundredth part, per¬ 
forms an important part in the act of vegetable nutrition, 
on account of the carbon that it contains. This body .is 
found, in large quantities, in plants submitted to decompo¬ 
sition or combustion. 
35. Carbonic acid, formed of carbon and oxygen, is de¬ 
composed, according to some naturalists, in the inner bark ; 
the carbon becomes fixed in the plants, and the oxygen 
escapes. This decomposition, however, cannot take place 
unless the plant is submitted to the influence of light; in 
the contrary case, the carbonic acid is expelled by the 
stems and the leaves, just as they received it. 
36. Thus we are taught that it would be highly impru¬ 
dent to sleep in an apartment containing many plants. 
The air, vitiated by the great quantity of carbonic acid dis¬ 
charged by the plants, might become exceedingly danger¬ 
ous to the sleeper. 
oxydes, there are some that restore the blue color that has been reddened 
by the action of acids. Their names differ, according to their degree of oxy¬ 
genation ; thus we say, protoxyde, deutoxyde, peroxyde of iron, agreeably 
to the degree of oxygenation of the metal. 
Salts are formed by the union of acids and oxydes ; and they derive their 
names from their constituent parts. If the termination of the acid is in ic 7 
it is changed into ate — if in ous, into ite. The name of the acid thus modi¬ 
fied is followed by the name of the simple body that enters the oxyde to form 
that of the salt; thus we will say, carbonate of lime, or carbonate of iron, 
agreeably as the carbonic acid shall have united itself with lime or iron to 
constitute the salt — sulphate of lime, or sulphite of lime, as we may have 
employed sulphuric or sulphurous acid to form the combination. 
QUESTIONS. 
1. What is the stem ? 
2. What is the trunk ? 
3. What is stubble ? 
4. What is a ligneous stem ? 
5. What is an herbaceous stem ? 
