VITAL FORCE IN SENSITIVE PLANTS— IN CHARA. 9 



the plant, the leaves gradually open ; but when touched they can no 

 longer be irritated so as to ooUapse, as they do in their natural condition. 

 They remain iu this passiye state, benumbed, as it were, for a consider- 

 able time, and generally it is not untU some hours have elapsed that 

 they regain their original sensibility. If, however, while ia this passive 

 state, the leaves be again touched with chloroform, they coUapse as 

 before. It is not till after several doses that they lose their sensibility 

 entirely, or at all events until the next day ; sometimes they wither 

 completely after too many applications of the chloroform. The purer 

 the chloroform and the greater the excitability of the plant, the greater 

 are the effects produced." 



Similar experiments with rectified ether gave results quite analo- 

 gous. When the author repeated the experiment with chloroform, he 

 found that the leaflets remained paralysed, as it were, and still unable 

 to open after eighteen hours' rest ; they seemed to be dead. This was 

 apparently caused by excess of chloroform, a laiger dose than that em- 

 ployed by Dr. Marcet having been used. It is thus seen that overdoses 

 of chloroform kiU. plants as well as animals, though small doses are 

 inaoouous. 



b. There grows commonly ia ditches and stagnant water a plant 

 called Chara, in the large cells of which a current of green globules 

 steadily rises up one side and falls by another, presenting an appearance 

 calling to mind the motion of an endless chain. If one of these cells is 

 choked by a Ugaioire, then the motion contiuues exactly as before in 

 each of the two divisions so produced. The singularity of the 

 motion, and the ease with which it may be observed, have rendered this 

 plant a favourite object of examination by young microscopists. Those 

 philosophers who refused to admit this to be a vital motion analogous 

 to that of the blood, imagined that they had found an explanation in 

 electrical action. But Dutrochet, who once held this opinion, when 

 he attempted to establish his hypothesis upon experiment, found that 

 the magnetic force, even when prodigious, exercises no influence 

 whatever upon the circulation of fluid within the cells of Chara, and he 

 was obliged to admit the presence of a vital force, of the nature of which 

 we are whoUy ignorant. Motion of an analogous nature has been now 

 remarked within the cells of so many plants that we cannot doubt it to 

 be a universal phenomenon. It is to be remarked that this kind of 

 movement is whoUy independent of the general motion of the sap. 



c. When a grain of pollen falls upon a stigma, it protrudes a tube of 

 extreme tenuity. The tube penetrates the stigma, much in the same 

 manner as the root of a seed pierces the earth. Thence it proceeds 

 unerringly to the tiny opening which it is destined to enter, passing by 

 all obstacles, turning to the right or to the left, and now ascending, 

 now curving back again, with the same constant certainty as would 

 attend an act of consciousness. Nor is this all ; in certain cases the 



