220 
It is known, for example, that if plants be put to ve- 
getate in a vessel filled with atmospheric air, depri- 
ved of its carbonic acid, and the vessel be then expo- 
sed to the sun, the plants continue to flourish, and the 
air experiences no change, either in purity or in vo- 
lume *. These experiments he repeated many 
times, and always found the plants to grow as well in 
air, from which the carbonic acid had been previously 
removed by lime-water, as in those cases where this 
operation had not been performed t ; from whence 
it necessarily follows, that the presence of carbonic 
acid in atmospheric air is not essential to the vegeta- 
tion of plants. 
500. But, from experiments of a different nature, 
M. de Saussure was led to draw an opposite conclu- 
sion. In vessels in which plants were placed to ve- 
getate, he suspended a quantity of lime, which had 
been slaked by water, and afterwards dried briskly 
at a boiling heat ; the vessels were, also, inverted in- 
to saucers of lime-water. After the second day, the 
atmosphere of the plants, exposed to the sun in this 
apparatus, diminished in volume. On the third day, 
the inferior leaves began to turn yellow : by the 
fifth day, they had all fallen, and the plants no long- 
er exhibited signs of vegetation. Their atmosphere, 
at this period, had lost in bulk three cubic inches 
of the fifty originally employed ; it was less pure 
than at first, but contained no carbonic acid. Some- 
times the plants died in two days, when thus expo- 
sed to the sun ; while others, confined in similar ves- 
* Annales de Chimie, t. xxiv. p. 136. f Ibid. p. 144'. 
