( 48°) 
1. In pure carbonic acid gas, seeds will swell, but: 
not germinate. 2. United with water, this gas has- 
tens vegetation. 3. Air containing more than one 
twelfth part of its volume of carbonic acid, is most: 
favorable to vegetation. 4. Turf, or other carbona- 
ceous earth, which contains much carbonic acid, is 
unfavorable to vegetation until it has been exposed 
to the action of atmospheric air, or of lime, &c. 5. 
If slacked lime be applied to a plant, its growth 
- will be impaired until the lime shall have recovered - 
the carbonic acid it lost by calcination. 6. Plants 
kept in an. artificial atmosphere and charged with 
carbonic acid, yield, on combustion, more of that 
acid than plants of the same kind and weight grow- 
ing in atmospheric air. 7. When plants are expo- 
sed to air and sunshine, the carbonic acid of the at- 
mosphere is consumed, and a portion of oxigen left 
inits place. If new supplies of carbonic acid be 
given to the air, the same result follows ; whence it 
has been concluded, that air furnishes carbonic acid 
io the plant, and the plant furnishes oxigen to the 
air. This double function of absorption and respi- 
ration, is performed by the green leaves of plaats.(1) 
8. Carbon is to vegetation what oxigen is to animal 
life; it gives support by purifying the liquids and 
rendering the solids more compact. 
AV. Of light, heat and electricity, and their agency 
in vegetation: 
When deprived of light, plants are pale, lax and 
dropsical ; restored to it, they recover their colour, 
(1) This was a discovery of Sennebier. 
