Cuar. IX.] CARBONIC ACID. 181 
meat placed on the glands of three leaves. One of these leaves hung 
a little down, and was at first partly and soon afterwards completely 
covered by the water, which rose within the vessel as the gas was 
absorbed. On this latter leaf the tentacles, to which meat had been 
given, became well inflected in 2 m. 30 s., that is, at about the normal 
rate; so that until I remembered that the leaf had been protected 
from the gas, and might perhaps have absorbed oxygen from the water 
which was continually drawn inwards, Į falsely concluded that the 
carbonic acid had produced no effect. On the other two leaves, the 
tentacles with meat behaved very differently from those on the first 
leaf; two of them first began to move slightly in 1 hr. 50 m., always 
reckoning from the time when the meat was placed on the glands— 
were plainly inflected in 2 hrs. 22 m.—and in 3 hrs. 22 m. reached 
the centre. Three other tentacles did not begin to move until 2 hrs. 
20 m. had elapsed, but reached the centre at about the same time 
with the others, viz. in 3 hrs. 22 m. 
This experiment was repeated several times with nearly the same 
results, excepting that the interval before the tentacles began to move 
varied a little. I will give only one other case. A plant was exposed 
in the same vessel to the gas for 45 m., and bits of meat were then 
placed on four glands. But the tentacles did not move for 1 hr. 40 m. ; 
after 2 hrs. 30 m, all four were well inflected, and after 3 hrs. reached 
the centre. 
The following singular phenomenon sometimes, but by no means 
always, occurred. A plant was immersed for 2 hrs., and bits of meat 
were then placed on several glands. In the course of 13 m. all the 
submarginal tentacles on one leaf became considerably inflected ; those 
with the meat not in the least degree more than the others. Ona 
second leaf, which was rather oid, the tentacles with meat, as well as 
a few others, were moderately inflected. On a third leaf all the 
tentacles were closely inflected, though meat had not been placed on 
any of the glands. ‘This movement, I presume, may be attributed to 
excitement from the absorption of oxygen. The last-mentioned leaf, 
to which no meat had been given, was fully re-expanded after 24 hrs. ; 
whereas the two other leaves had all their tentacles closely inflected 
over the bits of meat which by this time had been carried to their 
centres. Thus these three leaves had perfectly recovered from the 
effects of the gas in the course of 24 hrs. 
On another occasion some fine plants, after having been left for 
2 hrs. in the gas, were immediately given bits of meat in the usual 
manner, and on their exposure to the air most of their tentacles became 
in 12 m. curved into a vertical or sub-vertical position, but in an ex- 
tremely irregular manner; some only on one side of the leaf and some 
on the other, They remained in this position for some time; the 
tentacles with the bits of meat not having at first moved more quickly 
or farther inwards than the others without meat. But after 2 hrs, 
20 m. the former began to move, and steadily went on bending until 
they reached the centre. Next morning, after 22 hrs., all the tentacles 
