17H IXSKCTICIDES, FUNGICIDES, AND WEED KILLERS. 



may be chosen ; however, the best result would be obtained by applying 

 the treatment after cutting the grass. Mosses infest poor and moist 

 soil ; after their destruction by green vitriol the cause of their presence 

 should be obviated by manuring and draining [and liming]. 



2. On Trees. — To free the trunks of trees from mosses and lichens, 

 which are so many refuges for parasites, they are scraped with the 

 decorticator-moss-eradicator, then the trunk and branches are coated 

 with a solution of green vitriol. The stronger the solution the better, 

 but the strength of the green vitriol may be considerably reduced by 

 adding a corrosive acid, such as sulphuric acid ; in such conditions a 

 10 per cent solution of green vitriol containing 2 per cent of sulphuric 

 acid acts as well as a 40 per cent solution of green vitriol. By add- 

 ing 2 per cent of blue vitriol to this solution, the tree is freed from all 

 spores of fungi. 



3. 071 Boofs. — A 10 per cent solution of green vitriol spread on 

 moss-covered roofs completely destroys the moss. But green vitriol 

 cannot be used where there are zinc gutters, for the latter will be 

 corroded by contact therewith. 



Destruction of Dodder. — Dodder is a plant without chlorophyll, 

 which, like fungi, is more sensitive to the action of iron than green 

 plants. But if the filaments of the young plant do not resist 2 per cent 

 solutions, on the other hand a 10 per cent solution is required to kill the 

 adult plants, which often kills or injures the nurse plant. Schribaux's 

 tests have shown that dodder seeds, owing to their thick tegument, 

 resist 20 per cent solutions of green vitriol, and that even after steep- 

 ing for fifty days their vitality is not lessened. Immersion in water 

 for fifty days : 19 percent germinated. Immersion in 20 per cent solu- 

 tion of green vitriol for fifty days : 12 per cent germinated. Dodder 

 specially invades trefoil and lucerne fields, plants equally sensitive to 

 10 and 20 per cent solutions of green vitriol ; needless to say the treat- 

 ment should be applied before fructification and should not extend 

 over the whole field. It suffices to treat the parts attacked. Stronger 

 solutions of sure effect can thus be used. By sacrificing a few square 

 yards of the crop the spread of the plague can be averted. The 

 following is the best method of working : After mapping out the 

 dodder spots, comprising within the surface to be treated a radius of 

 a metre beyond that where the filaments are apparent, the spots are 

 cut with the scythe. It suffices then to water the diseased spots with 

 a 2 per cent solution of green vitriol if the treatment be carried out 

 in May ; on the contrary, if in July a 10 per cent solution will be 

 required. Needless to say if one watering be not enough, the opera- 

 tion is repeated a few days afterwards, and watering must be copious 

 so as to reach the matted filaments. Ponsard and Clerc advise this 

 treatment to be done in the spring. 



Use of Green Vitriol to Combat the Diseases of Plants. — 

 Chlorosis. — In certain conditions unfavourable to the plant, chlorophyll, 

 the active agent of assimilation, does not develop normally. A con- 

 dition of languor follows, which is manifested by a yellowish or reddish 

 coloration of all the green parts of the plant. This pathological con- 

 dition is known as jaundice, when it is caused by a want or excess of 



