on the Vegetable Kingdom. 301 



leaves had begun to grow yellow at the ends, the superior 

 leaves not being dead. On the 16th May, almost all the sur- 

 face of the two lower leaves had become yellow, and the 

 leaves were quite dry. The upper leaves were all withered, 

 but without any change of colour. 



PURPLE DIGITALIS. 



On the 10th May, at 9 h A. M. the root of a French bean 

 was introduced into a solution of six grains of this substance 

 jn an ounce of water. At the end of a few seconds there was 

 a slight crispness at the end of some of the leaves. In 

 the evening the ends of the leaves were withered, and in 

 twenty-four hours more the plant was quite dead. 



The two last poisons, when administered to animals, de- 

 stroy life by acting on the nervous system. 



From these experiments it seems to be satisfactorily de- 

 monstrated. 



1. That the metallic poisons act on vegetables nearly in the 

 same manner as they act on animals. They appear to be ab- 

 sorbed and carried into the different parts of the plant, and 

 alter and destroy the tissue of it by their corrosive power. 



2. That vegetable poisons, and particularly those which are 

 demonstrated to destroy animals by their action on the ner- 

 vous system, produce also the death of plants. But as we 

 can scarcely conceive that poisons, which do not in any way 

 attack the organic tissue of animals, could alter that of vege- 

 tables in such a degree as to kill them at the end of a few 

 hours, it appears to me very probable that there exists in 

 vegetables a system of organs which is affected by certain 

 vegetable poisons nearly in the same manner as the nervous 

 system. 



Mr Marcet concludes his very interesting memoir, by an 

 account of some experiments on the action of different gases 

 on the roots of vegetables. Carbonic acid gas was found to 

 exert a more deleterious action than hydrogen, and the action 

 of azote was much more rapid than any of the gases which he 

 tried. The nitrous oxide acted a little more rapidly than 

 hydrogen. 



