Irritability. 203 



Irritability, 



BY PROFESSOR LINDLEV. 



The vitality of plants seems to depend upon the existence of 

 an irritability which, although far inferior to that of animals, is 

 nevertheless of an analogous character. This has been proved 

 by a series of interesting experiments, by M. Marcet, of Geneva, 

 upon the exact nature of action of mineral and vegetable poisons. 

 The subject of his observations was the kidney bean ; and in 

 each experiment a contrast was formed between the plant ope- 

 rated upon and another watered with spring water. A vessel 

 containing two or three bean plants, each with five or six leaves, 

 was watered with two ounces of water containing twelve grains 

 of the oxide of arsenic in solution. At the end of from twenty- 

 four to thirty-six hours the plants had faded, the leaves drooped, 

 and had even begun to turn yellow. Attempts were afterwards 

 made to recover the plants, but without success. A branch of a 

 rose tree was placed in a solution of arsenic, and in twenty-four 

 hours ten grains of water and 1-12 of a grain of arsenic had 

 been absorbed. The branch exhibited all the symptoms of un- 

 natural decay. In six weeks a lilac tree was killed in conse- 

 quence of fifteen or twenty grains of moistened oxide of arsenic 

 having been introduced into a slit in one of the branches. Mer- . 

 cury, under the form of corrosive sublimate, was found to pro- 

 duce effects similar to those of arsenic ; but no impression was 

 made on a cherry tree by boring a hole in its stem and introduc- 

 ing a few globules of liquid mercury. Tin, copper, lead, muri- 

 ate of barytes, a solution of sulphuric acid and a solution of pot- 

 ash, were found to be all equally destructive of vegetable life ; 

 but it was ascertained by means of sulphate of magnesia that 

 those mineral substances which are innoxious to animals, are 

 harmless to vegetables also. In the experiments with vegetable 

 poisons, the bean plants were carefully taken from the earth and 

 their roots immersed in the solutions used. It had been pre- 

 viously ascertained that plants so transplanted and placed in water, 

 under ordinary circumstances, would remain in excellent health 



