144 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



plants every third day with a solution consisting of one part of sulphate 

 of copper in seven thousand parts of water. The check plants, which 

 were not watered with the copper solution, were indiscriminately mixed 

 with the treated plants. The watering was done during the afternoon, 

 .and the quantity used for each plant was sufficient to soak the soil 

 thoroughly. 



After a month's treatment all the Tomato plants were perfectly free 

 from disease. On the other hand, one or both cotyledons of thirty-fom 

 Cucumber plants showed blotches of the disease. At the same time a 

 ■considerable number of the untreated check plants, both Cucumbers and 

 Tomatos, were badly diseased. 



At this stage both treated plants and checks were sprayed with water 

 •containing the spores causing their respective diseases, and this- was con- 

 tinued weekly until the end of the experiments. Under this drastic 

 treatment all the untreated check plants, both Cucumbers and Tomatos, 

 were badly diseased during the following two weeks. 



After six weeks' treatment with the solution of sulphate of copper of 

 the strength indicated above, the strength was increased to one part of 

 sulphate of copper in six thousands parts of water, and the soil in which 

 the plants were growing was soaked every fourth day until the end of the 

 experiments, which lasted for eleven weeks. At the expiration of this 

 period both Cucumber and Tomato plants were bearing a good crop of 

 well-grown mature fruit. 



Not a single one of the Tomato plants treated with the sulphate of 

 •copper solution showed a trace of disease ; and in the case of the treated 

 Cucumber plants the disease never extended beyond the cotyledons, and 

 this notwithstanding the fact that badly diseased plants were growing 

 amongst the treated plants throughout the entire period. In addition to 

 this the treated plants were sprayed several times with water containing 

 spares of the fungus parasites in suspension. It now simply remained 

 to ascertain whether any of the copper taken up by the roots of the 

 plants had been deposited in the fruit. For this purpose specimens of 

 Tomatos and Cucumbers borne by treated plants were submitted to Dr. 

 Thorpe, C.B., F.R.S., Principal Chemist, Government Laboratory, who 

 reported as follows : 



" I have examined the samples of Tomato and Cucumber produced from 

 the plants treated with solutions of copper sulphate sent to me on the 

 4th instant, but there is no evidence that the amounts of copper present 

 are sensibly greater than are found in the fruits obtained from the 

 untreated plants. — (Signed) T. E. Thorpe." 



It is important to bear in mind the fact that the above method of 

 treatment for producing immunity against fungus parasites applies to 

 Cucumbers and Tomatos only, so far as direct experiments have been 

 carried out. A solution of sulphate of copper appears to have markedly 

 different effects on different kinds of plants. Luffa agyptkusa, Mill., a 

 close ally of the Cucumber, is killed by two waterings at a strength of 

 one in six thousand. Barley, on the other hand, remains perfectly healthy 

 when treated with one in five hundred, and in addition may become badly 

 attacked by its common parasite, Oidium gram in is, P. 



