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XIV. On the Respiration of the Leaves of Plants. 
By William Hasledine Pepys, Esq., F.R.S. 
Received April 8, — Read May 25, 1843. 
After i had written, in conjunction with my friend Mr. Allen, the papers which 
were published in the Philosophical Transactions for 1808, 1809 and 1829, on the Re- 
spiration of Man, the Graminivorous Animals and Birds, showing - the deterioration of 
the atmospheric air by the quantity of carbonic acid gas produced, I instituted a 
series of experiments on the respiration of plants, and particularly of their leaves. 
The difficulty of obtaining, for this purpose, specimens which had been previously 
accustomed to respire constantly under a glass inclosure, and to maintain all their 
functions in that situation, was overcome by my obtaining possession of a few fine 
specimens of fig- and vine-trees, which had been under glass culture for a number of 
years. 
To obviate the errors which might arise from making the experiments over water, 
the apparatus which I formerly used in the combustion of the diamond and other 
carbonaceous substances was employed, and a modification of the mercurial gaso- 
meters, with an appendage consisting of a pair of concave glasses, which formed, 
when united, an oblate spheroid, was found most useful in the investigation of the 
nature and chemical composition of the atmospheric air which had served the pur- 
pose, first of animal, and then of vegetable respiration. 
The pair of concave glasses above mentioned were secured in strong brass rims, 
well and accurately ground together ; and, to prevent their separating when in use, 
eight brass screws were attached to the rims. There were also three openings in the 
rims, for the purpose of forming a communication with the gasometers, and with the 
plant or leaf which was the subject of the experiment. 
The mercurial gasometers having been already described and figured in the paper 
published in the Philosophical Transactions for 1807, it will not be necessary here to 
repeat their description, but a representation of the oblate spheroid, in which the plant 
subjected to the experiment was confined, is given, in connexion with the mercurial 
gasometers, in the annexed Plate XVIII. 
The following is the journal of the experiments which I made with this apparatus : — 
July 16th, 1838. 
From a large mercurial gasometer, connected with the two smaller and the glass 
hemispheres, I passed 100 cubic inches of respired air, which I suffered to escape 
by one of the small gasometers after it had been through the hemispheres ; I 
