36 DISEASES OF CULTIVATED PLANTS 



the flowers is changed and the fruit remains small and 

 yellowish, with scattered reddish patches, and finally shrivels. 

 The root presents a normal appearance superficially, but 

 when carefully examined the vascular system is found to be 

 feebly developed, the amount of protoplasm is scanty in the 

 cells, and there is but little nitrogenous material present. 

 In the leaves the chlorophyll not only disappears, but also 

 the chloroplasts. In such leaves raphides and crystals are 

 very abundant. 



The primary cause of chlorosis is not definitely known ; 

 Viala strongly suspects the presence of carbonate of lime in 

 the soil as the agent. The disease only manifests itself in 

 vines growing in a calcareous soil. It is considered that 

 the carbonate of lime taken up in solution by the roots 

 precipitates the organic acids in the cells, and owing to this 

 precipitation, the carbonate of lime continues to be taken up 

 by the roots. I!y this means the normal acidity of the cell- 

 sap is diminished, and the normal feeble alkalinity of the 

 protoplasm is augmented. As a consequence the normal 

 activity of the cells is disturbed, and results in a diminished 

 formation of nitrogenous matter and of hydrocarbons. Viala 

 further demonstrated that the application of sulphate of iron 

 restored the green colour. The -round was watered in the 

 spring with a solution of sulphate of iron in water. 



The sulphate of iron is supposed to act bj converting the 

 soluble carbonate of lime into insoluble sulphate of lime 

 gypsum. 



Watering the foliage with one per cent, solution of sulphate 

 of iron in water also favours the formation of chlorophyll in 

 the leaves. 



S. Mokrzecki has recently been experimenting with sulphate 

 of iron as a cure for chlorosis; the following is his account 

 of the process and the results attained. 



In order to restore the trees to health, I In. red from one to 

 four holes in the trunk of the tree, i to i \ cm. in diameter, 

 and deep enough to put 4 to 1^ grammes of green vitriol 

 (sulphate of iron). These holes were smeared over with 

 cement. These little wounds readily heal towards the 

 autumn. The ascending sap carries up with it the iron in 

 solution to the tips of the leaves, and the trees begin to 

 improve wonderfully ; the bright green colour soon appears, 

 and in size and any other relation it is difficult to distinguish 

 them from those not affected. Other salts of iron (such as 



