89 
turn or face of the utriculi, for he could never find 
the distinct epidermis of Saussure. Bat whether this 
covering be, or be not, a distinct membrane, it is ad- 
mitted by all to be furnished with innumerable pores. 
In a leaf of the bulbous lily, Hedwig counted 577 
pores in the small space of a square line ; and M. 
Jurine reckoned 140 in the same space of a leaf of 
fritillary. These pores are in form either oblong, 
oval, or irregular ; and they extend, in different di- 
rections, over the surface of the leaf. Some leaves 
have them on both sides ; some, on one side only ; 
and other leaves are wholly destitute of pores. In 
the leaves of trees, they are chiefly distributed on the 
under surface, in the juniper on the upper, and in. 
the fir and larch they are found on both surfaces. 
All the parts of the flower are likewise furnished 
with them. When observed by the microscope, af- 
ter moistening the pellicles, the pores appeared to M. 
Jurine to be filled with a black matter, which was a 
small bubble of air contained in them ; for, by gen- 
tle pressure with a fine needle, the bubble was de- 
tached, and the part then became transparent. And 
when the pores of different pellicles, previously re- 
moved from the leaves, were compressed under wa- 
ter, the air that issued from them gradually disap- 
peared, which led him to conclude that it was carbo- 
nic acid. 
326. That these pores communicate with the utricu- 
lar interstices before described, he supposed from the 
following experiment. He placed the leaves of the 
geranium pelt at um and rumex sanguineus in water 
under the receiver of an air pump, and observed air 
