Physical Structure of Plants. : 53 
tub containing sufficient water to just cover them and not inter- 
fere with the functions of the plants; by moving the water with 
the hand, it softened and washed out the garden mould of the. 
tumblers, enabling me in afew minutes to remove each plant 
in a perfect state, without injuring a single spongiole.. The 
plants were next introduced into a suitable pneumatic trough, 
washed free from adherent air by passing the fingers over every 
part, and then drawn under a receiver with a wide mouth, where 
they were rapidly broken and gently pressed so as to obtain the 
free gases of their interior; the stem and leaves both furnished 
gas. These manipulations were conducted as rapidly as possible 
and the gas obtained immediately analyzed. 
13. The plan of analysis consisted of first passing the gas 
shines solution of potash in a Kemp’s tube, to ascertain the 
carbonic acid, then mixing with binoxide of nitrogen properly 
prepared for the occasion, to discover the oxygen, the resulting 
gas was examined for hydrogen and carburetted hydrogen in 
several cases but found to be pure nitrogen. 'The examination 
Was completed in about three minutes, amd no corrections for 
temperature, pressure, or moisture were necessary from the rapid- 
ity of the operations, and the whole being conducted in water of 
the same degree of heat. I confess my unwillingness to use the 
binoxide, but neither the eudiometers of Volta, Ure, or Hare 
could be employed with such small amounts of gas, and finally 
I became reconciled to this method by the excellent results which 
“May be obtained with a little care. Each series of examinations 
‘Was compared with an analysis of atmospheric air made immedi- 
ately after, and in 25 measures I find that the average amount of 
oxygen is 20-83 per cent., from which it never varied 0°20 vol- 
umes ; this result is equal to that of the elaborate analyses of 
and Boussingault, who obtained 20:8 per cent of oxygen. 
M4. Evvperiments.—Three analyses of the internal gas of the 
Datura plants, gave on the 15th of June, a mean of nitrogen 
_ 87-0, oxygen 13-0 per cent. with no. carbonic acid, and on the 
ith, three further examinations s gave nitrogen 88-0, oxygen 12-0 
and no carbonic acid. 
Two analyses of the gas. Fae giass ‘slants on the 15th, gave a 
mean of. nitrogen 84-2, oxygen 148 per cent., and on the 17th, 
Nitrogen 88-0, oxygen 12:0 without carbonic acid in either case. 
™ ee by Dr. ei — in. the Philosophical Maga- 
