MR. PEPYS ON THE RESPIRATION OF THE LEAVES OF PLANTS. 
331 
July 14th, 1840. — Barometer 30'300. Thermometer 59°. 
I repeated the experiment of the 19th of July, 1838, and, on the first examination of 
the respired air, found 6 per cent, carbonic acid, the respired air having - contained 
8 per cent, at the commencement. 
The process was then continued much quicker than before for twenty-five minutes, 
and on examination of the air, I found 5 per cent, carbonic acid. 
On examining - the respired air the next day I have generally found it reduced to 
2 per cent, carbonic acid. 
I repeated the experiment, using a fine healthy vine-leaf in place of the fig-leaf, 
and secured with the same precaution. I found the vine-leaf not so active an agent 
as the fig-leaf. The respired air, which at the commencement of the experiment gave 
7 per cent, carbonic acid, after two hours, and passing and repassing fifty times, 
on examination was found to contain 5 per cent, carbonic acid. 
A vine-leaf was secured in the glass hemispheres, and the small mercurial gaso- 
meters were supplied with atmospheric air, which was passed and re-passed at inter- 
vals for two nights and one day. On examining the atmospheric air that had been 
thus treated, I found that no carbonic acid had been formed, nor was there any 
alteration in the quantity of oxygen. 
A vine-leaf was secured in the glass hemispheres, the mercurial gasometers were 
connected, and the atmospheric air which they contained was passed and re-passed 
at intervals. At the end of fourteen days the leaf changed colour in patches of yellow, 
until, at the conclusion of three weeks from its introduction, it became almost entirely 
yellow. On examining the atmospheric air, I found that it contained 2 per cent, car- 
bonic acid, and nearly half an ounce measure of fluid had condensed in the hemi- 
spheres ; the addition of lime water to the fluid produced no turbidness. 
During the months of June and July, 1841, I pursued the same train of experi- 
ments upon the fig-leaves in the hemispheres of glass, as before described, using re- 
spired atmospheric air, and obtained similar results as to the abstraction of the car- 
bonic acid gas and the restoration of the oxygen. 
The trees were in good health and ripened their figs as usual. 
April 21st, 1842. — Barometer 30T82. Thermometer 62°. 
Having secured a fine healthy leaf of the fig-tree in the glass hemispheres connected 
with the mercurial gasometers, I passed 150 cubic inches of respired air, containing 
8 per cent, of carbonic acid gas, through the small gasometers and the hemispheres, 
and then liberated it. I then passed fifty-five cubic inches of the respired air from 
the large mercurial gasometer into the small one, and from thence through the hemi- 
spheres into the other small gasometer, and back again : on examining this air, I found 
8 per cent, carbonic acid gas. 
I then passed and repassed the air ten times, taking five minutes for each passage, 
and on examining the air found 6^ per cent, carbonic acid gas. The respired air was 
2 x 
MDCCCXLIII. 
