Chloroform on the Sensitive Plant, 131 



each branch*. At the end of one or two minutes, sometimes 

 more, according as the plant is more or less sensitive, most of 

 the leaves next to the chloroformed leaf and situated beneath it 

 on the same stalk, droop one after another, and their folioles 

 contract, although generally in a less complete manner than 

 those of the leaf placed in immediate contact with the chloro- 

 form. After a rather long time, varying according to the 

 vigour of the plant, the leaves open again by degrees; but on 

 trying to irritate them by the touch, it is seen that they have 

 become nearly insensible to this kind of excitement, and no 

 longer close as before. They thus remain as if torpid for 

 some time, and generally do not recover their primitive sen- 

 sitiveness till after some hours. If, however, when they are 

 in this state of apparent torpidity, they are subjected again to 

 the action of the chloroform, they close as they did the first 

 time. It is not till after they have been chloroformed several 

 times, that they lose all kind of sensitiveness, at least until 

 the next day ; sometimes they even fade completely at the end 

 of too frequent repetitions of the experiment. In all cases the 

 effects observed are the more marked in proportion to the 

 purity of the chloroform employed and the degree of sensitive- 

 ness in the plant. 



An analogous phasnomenon is produced if, instead of placing 

 the drop of chloroform on the base of the petiole, it is laid on 

 the folioles situated at the extremity of a branch. The folioles 

 of this branch immediately begin to close pair by pair, the 

 common petiole droops, lastly the folioles of the other branches 

 close in turn. At the end of two or three minutes, the nearest 

 opposite leaf, and if the plant is vigorous, most of th6 other 

 leaves situated below on the same stalk follow their example. 

 When, after some time, the leaves open again, the saii^e want 

 of sensitiveness is manifested as in the preceding case.? 



A singular feature in this phaenomenon is the manner in 

 which the action of the chloroform is propagated from one 

 branch to another, then from one leaf to another, even when the 

 liquid disappears by evaporation almost as soon as it is deposited. 

 This action, as we have just seen, appears to be communicated 

 from the leaf to the stalk, following in the latter a descending 

 direction; generally the leaves situated beneath the chloro- 

 formed leaf are not at all affected. DeCandolle, in making 

 an analogous experiment on a sensitive plant with a drop of 

 nitric or sulphuric acid, remarked, on the contrary, that it 

 was the leaves above the leaf touched which closed, without 



* I previously convinced myself by experiment that a drop of water, 

 placed delicately on a leaf of the sensitive plant, caused no movement. 



K 2 



