Cuar. IX. CARBONIC ACID. 221 
same leaf. A single tentacle moved after 1 hr. 28 m.; after 
2 hrs. 8 m. several were inflected; and after 3 hrs. 3 m. all the 
seven tentacles with meat were well inflected. From the slow- 
ness of these movements it is clear that this leaf had been 
rendered insensible for a time to the action of the meat. A 
second leaf was rather differently affected; bits of meat were 
placed on the glands of five tentacles, three of which were 
slightly inflected in 28 m.; after 1 hr. 21 m. one reached the 
centre, but the other two were still only slightly inflected; after 
3 hrs. they were much more inflected; but even after 5 hrs. 
16 m. all five had not reached the centre. Although some of 
the tentacles began to move moderately soon, they afterwards 
moved with extreme slowness. By next morning, after 20 hrs., 
most of the tentacles on both leaves were closely inflected, but 
not quite regularly. After 48 brs. neither leaf appeared injured, 
though the tentacles were still inflected; after 72 hrs. one 
was almost dead, whilst the other was re-expanding and 
recovering. 
Carbonic Acid.—A plant was placed under a 122-oz. bell-glass 
filled with this gas and standing over water; but I did not make 
sufficient allowance for the absorption of the gas by the water, 
so that towards the latter part of the experiment some air was 
drawn in. After an exposure of 2 hrs. the plant was removed, 
and bits of raw 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 2m. 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, I 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 plaved 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 varicd a little. I will give only one other case, 
