Em Dr. Herne on the Deoxidation of 
my habitation has hitherto prevented me from attending to it at 
an earlier hour in the morning. Ihave, however, but little doubt 
it will be found as acid as I have described it to be in India. 
I need scarcely observe, that the acidity which these leaves 
possess in the morning cannot be ascribed to any thing else than 
to the oxygen which the plant has absorbed during the darkness. 
. of the night, or which has been transferred from other constituent 
principles of the plant during that period. I think it has been 
absorbed, as it is so loosely united to its base, that even the light 
of the day has an immediate effect of disengaging it again. 
Doth Priestley and Ingenhousz have concluded, from numerous 
experiments, that all plants exhale vital air in the day-time, and 
fixt air or carbonic acid gas during the night; but these con- 
clusions have been called in question by some, from tlie various. 
results of experiments since made on this subject. What I have 
now related is therefore not destitute of interest,as it seems in- 
controvertibly to establish the theory of these celebrated philo- 
sophers. | 
I was in hopes of learning something new or pertinent on this 
interesting subject in Sprengel's work on the Structure and Na- 
ture of Plants: but, to my great disappointment, there is no- 
thing to be found but what has been advanced by the two phi- 
losophers just mentioned, and by Saussure and Sennebier in later 
times. | 
Sprengel expatiates much on the exhalation and absorption of 
carbonic gas, and only once mentions oxygen, when he notices. 
Sennebier's observations ; according to which, more carbonic gas 
is exhaled by plants during the night in close vessels, than there 
ijs oxygen disengaged in sunshine, 
: I beg leave further to observe, that the plant above treated of is, 
1n my opinion, truly a species of Cotyledon, with which it perfectly 
agrees 
