1878.] On the Transpiration of Plants. 161 
rated at the rate of g ounces per diem, and a vine with twelve 
square feet of leaf surface, transpired at the rate of 5 to 6 
ounces per day. The sunflower during a dry night lost 3 ounces, 
but nothing on a dewy night. The method adopted in these 
experiments is not referred to by him. 
Balfour, in his work on botany (page 457), refers to the investi- 
gations of Woodward, giving some of the results of this observer. 
Woodward took plants, and, having immersed their roots in 
water, placed them in the light for more than a month. He no- 
ticed the quantity of water absorbed and the amount transpired 
(making allowance for extraneous evaporation), and showed that 
the greater quantity of the water absorbed was again given off 
by the leaves. 
It is questionable whether results thus obtained are to be relied 
upon, inasmuch as these plants must have been placed under un- 
natural conditions and influences, by allowing their roots to rest 
in pure water; for it is a known fact that certain plants (Calla 
ZEthiopica, for instance) can be made to distill the water in drops 
from their leaves, if too abundantly supplied to their roots. 
Curiously enough, in every instance in which the methods 
adopted have been detailed, the objectionable circumstance of 
placing the plants in a very unnatural state while experimenting 
upon them has obtained. Reference is here made only to ex- 
periments on entire plants. The results of the observations 
of Garreau (Annales des Sciences Nat. 3d Ser. Bot. xiii. 35 5) on 
the transpiration from leaves should, doubtless, be accepted as 
reliable, if we consider the means employed: This observer esti- 
mated the amount of exhalation by collecting it by means of 
chloride of calcium, placing the leaf between two bell-jars, one 
applied to its upper and the other to its under surface. His con- 
clusions were: 
“1. The quantity of water exhaled by the upper and under 
surfaces of the leaves is usually as 1 to 2, I to 3, or even I to 5 
or more. The quantity has no relation to the position of the 
surfaces, for the leaves when reversed gave the same results as 
when in their natural position. 2. There is a correspondence 
between the quantity of water exhaled and the number of stomata. 
= 3. The transpiration of fluid takes place in greater quantity on- 
the parts of the epidermis where there is least waxy or fatty mat- 
_ ter as along the line of the ribs.” 
