754 



culiar evidences of irritability. The researches and experiments of 

 M. Marcet, Drs. Christison and Turner, and M. Macaire, lead to this 

 conclusion: the latter gentleman's experiments on the sensitive plant 

 {Mimosa pudica) are so interesting, that they will bear repetition 

 here, even though some of our readers may be already well acquaint- 

 ed with them. 



" Experiments were now made with this vegetable {Mimosa pu- 

 dica). When a leaf of this plant is cut, and allowed to fall on pure 

 water, the leaflets generally contract rajndly ; but after a few mo- 

 ments expand, and are then susceptible of contraction by the touch 

 of any other body. They may thus be preserved in a sensible state 

 two or three days. If the section be made with a very sharp instru- 

 ment, and without concussion, the leaves may be separated without 

 any contraction. The branches of this plant may be preserved for 

 several days in fresh water. Gum-water also effects the same purpose. 



" When a cut leaf of this plant falls upon a solution of corrosive 

 sublimate, the leaf rapidly contracts, and the leaflets curl up in an 

 unusual manner, and do not again expand. When put into pure 

 water, the sensibility does not return, but the whole remains stiff and 

 immovable. A little solution of corrosive sublimate being put into a 

 portion of pure water, containing an expanded branch of the plant, 

 gradually caused curling up of the leaves, which then closed and fell. 

 If the solution be very weak, the leaves open on the morrow, and are 

 still sensible, but ultimately contract, twist, and remain stiff till they 

 die. Solutions of arsenic and arseniate of potash produce the same 

 effects. 



" A leaf of the sensitive plant was placed in a cold, diluted solution 

 of opium: in a few moments it opened out as in water, and, after 

 half an hour, gave the usual signs of contractibility. In six hours it 

 was expanded, and had a natural appearance, but could not be ex- 

 cited to move. The leaflets were flexible at the articulations, and 

 offered a singular contrast to the state of irritation produced by cor- 

 rosive sublimate. Pure water did not recover the plant. A large 

 branch, similarly situated, expanded its leaves ; but in half an hour 

 had lost much of its sensibility : the leaflets, though alive, seemed 

 asleep, and required nuich stimulating to cause contraction. In one 

 hour the contractions ceased : in two hours the branch was dead. 



" A leaf placed in Prussic acid (Scheele's strength) contracted, 

 then slightly dilated, but was quite insensible, and the articulations 

 were flexible : water did not recover it. If the acid be very weak, 

 the leaflets dilate and appear to live, but are insensible. A drop of 



