162 On the Transpiration of Plants. [ March, 
Among the reported results that my eye has been able to reach, 
the foregoing only are considered worthy of special notice. - Pos- 
sibly some have escaped notice. 
The present experiments have been performed more especially 
with the view of ascertaining, as nearly as possible, the amount 
of water evaporated by plants in a healthy, natural state, and, also, 
to determine the connection between the meteorological con- 
ditions and variations and the nature of the cortical tissue, and 
transpiration. The importance of keeping the plants in a per- 
fectly normal state while being experimented upon was called at- 
tention to by Prof. Rothrock when lecturing on the subject of evap- 
oration from plants. To accomplish this it was suggested by him 
at the time that something impervious to moisture be adjusted to 
the receptacle in which the plant had previously been growing, fit- 
ting the same accurately to the base of the stem, the object of it 
all being to prevent any evaporation from the vessel or earth in 
which the plant was situated, so that all evaporation would be 
from the plant itself above the ground. The plant was now to be 
weighed at stated intervals and the loss of weight in any given 
time would represent the weight of the liquid transpired. It is 
evident that this, with properly balanced scales, would show ex- 
actly the quantity evaporated, save the slight increase in weight 
of the plant by the gases derived from the air which it fixes in 
the time of one experiment. This certainly must be regarded as 
extremely small when we reflect that plants return to the atmos- 
aere the greater portion by volume of the gases absorbed by’ 
them. The circumstance of plants gaining slightly in the course 
of a day by the gases they fix from the air, it will be observed, 
is not calculated to favor an over-estimate of the quantity trans- 
pired. . 
_ The means employed to accomplish these ends were as follows: 
ai 7 A : Sets i A 
E AEE T S AE EA E, O E r EEE ET g A RRS PETR OE a 
A piece of good rubber cloth of sufficient size was taken and 
its narrower border tucked up neatly around the base of the stem 
of the plant and secured by means of an elastic cord. The rubber 
_ cloth was then allowed to drop down over the vessel in which 
_ the plant was situated, the portion of the cloth underneath the pot- 
gathered up and brought to one side of its base, and after giving- 
ita few twists in one direction so as to insure its close application 
_ to all parts of the pot, the twisted portion was well wrapped an 
— > off 7 means ofa cord so as to a it in this conor. Thi 
