902 REV. G. HENSLOW ON TRANSPIRATION 
To this general property of transpiration the “ chloroleucites," 
or chlorophyll-grains, add their quota by means of the particular 
rays absorbed by them in sunlight. This second phenomenon, be 
it observed, is much more intense than the former, and Tieghem 
proposes the term “ chlorovaporisation " to represent the “ trans- 
piration chlorophyllien." 
II. TRANSPIRATION IN A SATURATED ATMOSPHERE. 
M. Dehérain states * that transpiration continues indefinitely 
in a saturated atmosphere from living leaves undetached from 
the plant; whereas (he says) a cotton wick dipped in water 
after two hours lost ‘076 gramme, after three hours’ exposure 
to sunlight ‘086 gr., but after four hours there was no further 
loss. Wiesner also remarks that plants can transpire in a 
saturated atmosphere, but only under the influence of light, 
inasmuch as the temperature within the leaf must be warmer 
than without, and this increase is produced by the conversion 
into heat of the rays which are absorbed. 
On the other hand, M. Leclere, in his paper alluded to above, 
states that transpiration does not take place in a saturated atmo- 
sphere. 
Lastly Knop (Veg. Stat. vi. 255) found that a moist piece of 
paper or wood lost weight when kept for some time in a confined 
space over water. 
The following experiments were made for the purpose of test- 
ing these results, and, as far as they go, they certainly seem to 
corroborate Dehérain and Wiesner with regard to transpiration, 
and Knop in that a dead substance will continue to evaporate 
for many days in an apparently saturated atmosphere. 
The experiments were conducted in a large glass jar con- 
structed like a hat with a broad rim. A thick piece of plate 
glass was well luted to the rim by a band of putty about two 
inches broad and a quarter of an inch thick. A small hole, about 
half a line in diameter, was bored in the centre of the plate, 
through which a fine platinum wire was passed, and upon which 
was suspended the leaf or cotton-wool &c. The wire was attached 
to one of the pans of a delicate balance, and, except when the 
specimen was required to be. weighed, the hole was plugged 
with putty. The latter was removed at intervals, so that the 
* Ann. des Sci. Nat. 5 sér. tome xii, 1869, p. 9. 
