Action of Metallic Poison on Vegetation. 413 



different poisonous substances. Having spread 256 grains of arseni- 

 ous acid upon a bed of earth of 64 feet of surface, the germination, 

 as well as the maturation of the seed went on as usual, without the 

 possibility of discovering a trace of arsenic in the plants submitted 

 to the experiment. 



If the soil is charged with too great a quantity of arsenious acid, 

 if it contains 1,200 grains upon the same space of ground, the seeds 

 merely commence the germinating process. They then contain 

 a sensible quantity of arsenious acid. In the same way, the author 

 has seen plants perish after some days, which had been watered with 

 a strong solution of corrosive sublimate. Analysis demonstrated, that 

 they contained mercury. The author having impregnated the soil 

 successively with arseniate of potash, arsenic, acid, tartrate of potash, 

 and antimony, the plants grew, but in one of the experiments, the 

 arseniate had become almost entirely insoluble in the soil; without 

 doubt it had been converted into arseniate of lime by the reaction of 

 the carbonate of lime upon the arseniate of potash ; the antimonial 

 salt in another experiment became almost completely insoluble. 



The same resulted in the moderate employment of acetate of 

 lead, sulphate of zinc, proto-nitrate of mercury, and bichloride of 

 mercury, without doubt for the same reason. 



In a soil impregnated with sulphate of iron, the plants indicated 

 more iron than those raised in a normal soil. In the same way 

 copper has been met with in those which had been sown in earth 

 charged with sulphate of copper, whilst a comparative study has 

 not discovered a trace amongst the vegetables grown naturally. 



This experience agrees with those tried by other learned men, 

 from which it results that the coppery or ferruginous matters can 

 penetrate into the plant, whether in the state of carbonate dissolved 

 in water charged with carbonic acid, or whether in a state of oxide 

 dissolved by the assistance of certain elements of the earth. 



In examining with care these different experiments, they authorise 

 the conclusion, that poisonous metallic compounds are not absorbed 

 by plants unless in a condition to become soluble ; that when they 

 are absorbed, germination is found to be suspended. 



That metallic compounds not poisonous, such as iron, appear to 

 be more easily absorbed than others, although the sulphate of iron 



