330 
MR. PEPYS ON THE RESPIRATION OF THE LEAVES OF PLANTS. 
then admitted fifty-two cubie inches from the large gasometer to one of the small 
ones; I then passed and repassed the respired air several times through the hemi- 
spheres, and on examination found it to contain eight parts in the 100 of carbonic 
acid. 
July 19th. — Barometer 30-220. Thermometer 72°. 
I enclosed with great care a fig-leaf between the glass hemispheres, and secured 
the stem by a grooved split cork, cemented by a strong solution of gum-arabic ; I 
then passed 100 cubic inches of respired air (containing eight parts in the 100 of 
carbonic acid) through the hemispheres containing the fig-leaf, and let that air 
escape; I then received into one of the small mercurial gasometers fifty-three cubic 
inches of the respired air, and passed it through the hemispheres into the other small 
mercurial gasometer ; from thence it was returned, and on examination was found 
to contain 8 per cent, carbonic acid. I then passed and repassed the respired ait- 
over the leaf in the hemispheres, allowing five minutes for each passage. After ten 
repetitions in this way, I examined the state of the respired air, and found 6 per cent, 
carbonic acid. I had used in the examination eight cubic inches. The forty-five cubic 
inches of respired air was now passed and repassed, as before, over the leaf in the 
hemispheres ten times, five minutes being allowed for each passage. The respired 
air was then examined, and found to contain 5 per cent, carbonic acid. The respired 
air was then left in the hemispheres and the two small gasometers until the next 
morning, at 1 1 o’clock ; on examination it was found to contain 3 per cent, carbonic 
acid. Many more experiments were made that same year, and with little variation 
in their results. 
July 4th, 1839. — Barometer 30'200. Thermometer 74°. 
I repeated the experiment of the 19th of July, 1838, with the same care and atten- 
tion. On the first examination of the respired air after ten passings and repassings 
over the fig-leaf in the glass hemispheres (five minutes being allowed for each pass- 
age), the respired air containing 8 per cent, carbonic acid at the commencement, 
I found 6 per cent, carbonic acid, two parts having disappeared. 
The process was then continued as before described, and on the second examina- 
tion I found 4^ per cent, carbonic acid in the respired air. The next morning, the 
air having been left as before, and the fig-leaf having remained in the hemispheres 
connected with the two small gasometers, I found on examination, 2^ per cent, car- 
bonic acid. 
It may be requisite here to state, that the respired air which was left after the 
action of the fig-leaf, was also examined by the charged solution of green sulphate of 
iron and nitrous gas, as to its quantity of oxygen, and gave the usual volume of 
oxvgen for the carbonic acid gas that had disappeared. 
The above experiments were repeated with little alteration in their result. The fig- 
leaves that had been confined in the air were all in as good health as the others on 
the same tree. A mark had been kept upon them, and I sometimes used the same 
leaf again. 
