98 
the kaf may, for a long time, be kept in life, yet it 
neither grows, nor produces any new vegetable mat- 
ter, when it is separated from the stem. In many of 
the experiments, however, of Ingenhousz * and Se- 
nebierf, oxygen gas was not only produced by the 
leaf after it was detached from the plant, but even af- 
ter it had been cut into small pieces, or was so much 
withered as to be unable to support an erect posture. 
When, indeed, it was beaten to a pulp, Dr Ingen- 
housz did not find it capable of affording pure air ; 
but this only shews that a certain state of vegetable 
organization is necessary to the discharge of this of- 
fice, but does, by no means, prove, that it is perform- 
ed by the vegetative function of the plant. 
338. Dr Ingenhousz himself, indeed, attributed 
the salutary influence, which plants exert on the air, 
to the direct light of the sun, conjoined with a certain 
state or condition of the vegetable structure, but not, 
in any degree, to vegetation, as such. At first, in- 
deed, he believed it to depend on vegetation ; but if 
vegetation, he adds, were the cause, plants should 
produce the same effects at all times, and in all situa- 
tions, where they are able to vegetate ; but they live 
and grow, to a certain size, in darkness, where they 
neither afford good air, nor possess the power of inv 
proving that which is bad J. Since, then, it appears, 
that the production of oxygen gas by plants takes 
place independently of vegetation, and without the 
* Exper. torn. ii. p. 166. 
f Mem. Phys. Chim. torn. i. p. 118. 
J Exper. torn. i. p. 4>8. torn. ii. p. 35. 
