GREEN VITRIOL. 179 



water ; etiolation, when it is produced by the want of light ; chlorosis, 

 when it is due to the want of iron. (This condition has some analogy 

 with the anaemia of man.) But the absence of potash may induce the 

 same phenomena. An excess of carbonate of lime in the soil,^ in- 

 sufficient nourishment, a defective condition of the roots," a patho- 

 logical condition of the whole plaat,^ insufficient heat, are so many 

 causes which may produce a chlorotic condition of the plant. Hence 

 it is easy to understand that iron cannot always remedy these diseased 

 conditions. It can only be of real service where the chlorisis is due to 

 a want of iron, or to an excess of lime,'* and of minerals rich in un- 

 assimilable potash. In jaundice and etiolation it would be of no use. 

 In the case of a tree attacked by chlorosis, the cause must above all 

 be carefully determined and iron only used well to the purpose. 

 Where chlorosis is due to a want of iron, the use of iron salts is to be 

 prescribed, and they will yield always a green coloration in a short 

 interval as well as give new vigour to the plant. The dose to use 

 varies in different cases. There are numerous methods which are 

 more or less effective, and which act more or less rapidly. 



1. Application of Green Vitriol to the Soil. — The most usual 

 method is to spread green vitriol in crystals around the tree in doses of 

 1-2 kilogrammes (2-2-4-4 lb.) per tree, and preferably after a heavy rain. 

 The dose is of no great matter ; an excess of green vitriol would not 

 injure the tree, as it is converted into insoluble derivatives in the soil. 

 Used thus its action is slow but durable. To get a more prompt effect 

 it is better to act thus : A circular trench is dug round the tree, at a 

 distance from the trunk, varying with its size, from 20-40 inches 

 and a width of 8-12 inches. After well watering it, 1-2 lb. of 

 green vitriol in crystals are sprinkled into it, or better still, a mixture 

 of manure and green vitriol in powder ; the soil is filled back into the 

 trench and copiously watered. It is preferable to dig out a basin 

 around the diseased tree and to fill in 10-20 litres (2-2-4 -1 gallons) 

 of a 10 per cent solution of green vitriol (Tome) or a 5 per cent 

 (Guirand). By repeating this treatment several times, every eight 

 days, the cure will be rapid and complete, and the action will be 

 more prompt as the tree is more in sap. The dose to use 

 which in certain cases may be very weak (Sorauer advises a solution 

 of 100 grammes of green vitriol, 30 grammes of saltpetre, and 20 

 grammes of phosphate of potash per tree), ought, on the other hand, 

 to be very stiong if the soil is calcareous. When carbonate of lime 

 is the predominating cause of chlorosis, as is the case with trees 

 with seed pips, such as the pear, and more especially the vine, 



1 Viala has shown that a vine in pot treated with 2 kilogrammes (4-4 lb.) of lime 

 became chlorotic in forty days. 



- Dementjew having found different acari on the roots of trees attacked by 

 chlorosis attributed that disease to their presence. 



3Raux bslieves he observed micro-organisms in plants attacked by chlorosis. 



■* According to Dementjew's experiments an excess of carbonate of lime would 

 only induce chlorosis when there was a lesion of the roots, a healthy root being 

 only able to absorb a normal amount of lime ; barium chloride as well as common 

 salt produce chlorosis under like conditions ; it would thus be the acari which he 

 found on the roots which by producing lesions were the prime cause of the chlorosis 

 of the tree. 



