1204 INSECTICIDES, FUNGICIDES, AND WEED KILLEES. 



table proves that copper salts do not act throufjjli their acids, as 

 Moiiselice asserts, but by their copper. The follo\vin<f are the suc- 

 cessive phases through which a plant, placed in a medium containing 

 a poisonous dose of blue vitriol, passes : If a branch of crj^ptomeria, 

 of Pinus or of Thuya, is dipped in a 001-0-05 per cent solution of 

 sulphate of copper, the chlorophyll contracts and ruptures and the 

 interior of the cell browns. If young plants be placed therein the 

 roots at first turn white, then become yellow and brown, grow up ab- 

 normally, then die. By analysing the different organs of a plant killed 

 by a solution of blue vitriol, Devaux found traces of copper in all its 

 parts. E. Otto, who submitted some plants {Pliaseolus vulgaris, 

 Triticum rulgare, Zea Mays, Pisum sativum) to the action of blue 

 vitriol in a nutritive solution, found, on the other hand, that these, in 

 spite of the deformation of their roots and their diseased state, only 

 contained a very little copper in the roots and none at all in the aerial 

 pai'ts. Hence he concluded that blue vitriol is so poisonous to the plant 

 that as soon as it has penetrated into the cells of the root it there oc- 

 casions such disturbances that the plant dies before it can be conveyed 

 further. 



This conclusion may be a sound one when the plant is placed in 

 contact with large quantities of a copper soluble salt, because in such 

 conditions the living cell is opposed to the osmosis of the salt. Nageli 

 also believes that blue vitriol kills the cell as soon as it is absorbed by 

 it, but that the latter does not suffer so long as it can prevent its pene- 

 tration. Nageli experiments on a green, fresh-water alga, Spirogyra, 

 which possesses, like phanerogams, chlorophyll and plasma, showed 

 that a solution of blue vitriol of 1 part in 100,000,000 sufficed to cause 

 the death of this alga. The effects produced on the chlorophyll and 

 the plasma are very visible under the microscope. The conditions 

 which we create artificially in a culture liquid do not exist, however, 

 on the large scale, and it would be rash to conclude by analogy that 

 blue vitriol acted in the same way on plants giown in the open field. 

 If the soil be watered with a solution of blue vitriol, chemical reactions 

 •ai-e produced between this salt and the soil which convert this soluble 

 salt into one or more insoluble compounds, and copper salts being more 

 poisonous the greater their solubility, insoluble salts such as oxide of 

 copper have no action on the plant. It is not necessary to go far to 

 find an analogous example. Mercury as bichloinde, a soluble salt', 

 poisons man even in very small quantity. It no longer has any in- 

 jurious action when it is absorbed as calomel, an insoluble product. 

 These two salts, however, possess the same elements, chlorine and 

 mercury, but their different action on the organism lies in the fact that 

 corrosive sublimate, being soluble, coagulates albumen, whilst the 

 insoluble calomel passes through the organism without causing any 

 trouble. Similarly the plant shows signs of poisoning in presence of 

 blue vitriol, because the latter is soluble and capable of producing 

 copper albuminates, but it remains indifferent to the presence of insol- 

 uble copper compounds on the large scale. When solutions of blue 

 vitriol are spread round a plant this salt all falls into the soil, and the 

 roots are no longer in contact with a poisonous and corrosive liquid 



