Chap. IX. CARBONIC ACID. 221 



same leaf. A single tentacle moved after 1 hr, 23 m. ; after 

 2 lirs. 3 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 

 8 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 hrs. 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. 



Carho7nc 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 comi3letely 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, 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 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. 



