168 Dr. H. Johnson on a Property in Plants, 



that they become curled up in circles or spiral coils. Every 

 one has seen an instance of this sort in the case of common 

 celery when dressed for the table. More remarkable proofs 

 of stimulation are, however, afforded in the following experi- 

 ments. 



Exp. 5. Several pieces of the stems of different plants 

 were divided, and, in a state of divergence, were immersed in 

 hot water. The divergence was at first increased in all, but 

 in a few minutes they entirely collapsed ; and their divergence 

 was totally destroyed. 



Fig. 3. 

 Exp, 6. I procured a young and 

 vigorous flower- stalk of the Common 

 Dandelion {Leontodon Taraxacmn) 

 which curved considerably to the left 

 side, fig. 3. Several notches («, «, «, «,) 

 were then made in the concave side, ex- 

 tending towards the axis of the flow- 

 er-stalk. The latter instantly became 

 erect ! and, on cautiously applying a 

 red-hot poker near to the entire side, 

 the fibres in the latter appeared to be 

 contracted,and the stem was now drawn 

 towards that side {i, e, to h\ the right ; 

 namely, the opposite to that to which 

 it inclined at first. 



Having concluded from the arguments above stated (pp. 166 

 and 167,) that divergence is the result of a living or vital action, 

 we learn, from Experiments 3 and 4, that it is entirely de- 

 stroyed by poisons, which is what might be expected to take 

 place if this supposition were well founded. If to this any 

 one should object, that even physical properties such as elas- 

 ticity, that of a quill for example, may be destroyed by poi- 

 sonous liquids which have also chemical effects; I answer, 

 that the objection has been already foreseen, and is in my 

 opinion completely refuted, by the fact, that similar effects 

 are produced by laurel-water, and even by sulphuretted hy- 

 drogen gas, which have little chemical activity. 



There can be no doubt, therefore, that poisonous liquids 

 act on plants as vital agents in the same way as that in which 

 they would act on the living system of animals*. When it is 

 proved, also, by Experiments 5 and 6, that stimulants act on 

 parts endowed with this property, just as they would do on 



• It appears from Dr. Christison's Work on Poisons, that it occasionally 

 happens when these agents are taken into the stomach that the contracti- 

 lity of the muscles is destroyed. 



