87 
which were cut in pieces and exposed in water to 
the sun, he observed very pure air to issue, in con- 
tinual jets, from their parenchymatous structure ; 
but in other plants, which afforded air very abun- 
dantly, its escape was not visible from either surface 
of the leaves *. 
323. M. Senebier also' found ' the inferior surface 
of the leaves to yield the most air ; that the epider- 
mis, when removed from the other parts, afforded 
no air, but that the air then issued abundantly from 
the denuded parenchyme ; wherefore he concludes, 
that the parenchyme is the true seat of the air that 
is obtained. The air, which thus exists in the pa- 
renchyme, he supposed to escape through the epi- 
dermis ; for when the surfaces of the leaves were 
covered with paste or varnish, no air then issued; 
but he was never able to discover the pores or ori- 
fices through which it obtained a passage f. The 
foregoing observations and experiments seem to 
prove that the gaseous fluids of plants exist princi- 
pally in the parenchyme of the vegetable, and from 
thence issue into the surrounding atmosphere* 
324. According to M. Jurine, the parenchyme of 
the leaf is composed of an aggregation of small cells 
or ittriculi) in which a green juice is contained. The 
form of these cells is either spherical, cylindrical, 
elongated or irregular ; and according to their form, 
the spaces between them, which he calls utricidar 
interstices, will be more or less large. It is in these 
* Exper. torn. i. p. 12. 24. 26'. 
t Mem* Pbysico-Chimicjues, torn i. p, 128, et seq. 
