69. ALL that has been hitherto said, with regard 
to the changes induced on the air by plants, bears 
an immediate reference to the agency of the leaves^ 
and of other green parts, in effecting these changes. 
But other parts of living vegetables produce, likewise, 
changes in the air, and these, in the next place, we 
propose shortly to consider. 
^70. Dr Priestley confined a full-blown rose in a- 
bout eight cubic inches of atmospheric air, contained 
in a small glass jar inverted in water. On exami- 
ning the air the next day, by the test of nitrous gas, 
he found it to be much depraved ; and, by the fol- 
lowing day, it was still farther depraved, but the 
flower, when \vithdrawn on the third day, did not 
seem to have lost any of its fragrance *. M. Scheele 
found, that, by confining fresh roots, fruits, herbs, 
flowers, and leaves, in separate vessels of common 
air, one-fourth part of the air was changed, in a fe\v 
days, into carbonic acid gas ! 
271. Dr Ingenhousz placed some flowers of man- 
gold (calendula) beneath an inverted vessel of atmos- 
pheric air, and left them all night in his chamber. 
The next morning, a portion of the air was examined, 
and found to be incapable of supporting flame ; it suf- 
fered, also, but little diminution when mixed with ni- 
trous gas. He then exposed the vessel, with the remain- 
* Obs. on Air, vol. iv. p. 3-11. 
f On Air and Fire, p, 15O. 
