22 The Spraying of Plants. 



duced black, velvety spots upon the foliage, and in 1880 it also 

 deformed the fruit to a considerable extent. The cause of 

 the injury was attributed by Prillieux, 1 the inspector-general 

 of Agricultural Education, to Fusicladium pyrinum ( Cladosporium 

 dendriticum, Walr.), and a description of the fungus was pub- 

 lished. Paul Oliver 2 made some experiments which were de- 

 signed to throw light upon the best method of destroying the 

 spores of the parasite. The materials used were, (1) pure water ; 

 (2) water acidulated with one-twentieth its amount of sulphuric 

 acid ; (3) a 33| per cent solution of the sulphate of iron ; (4) a 

 16f per cent solution of the sulphate of copper. He advised the 

 use of the last in rainy weather, but during dry weather either 

 the second or the third would prove effective. Oliver further 

 states that he succeeded in killing the spores of F. pyrinum with 

 an 8 per cent solution 8 of copper sulphate, and that he sprayed 

 his trees with a 10 per cent solution during the winter of 1882-3. 



This discovery that the salts of copper would prevent the 

 germination of the spores of fungi was by no means new. As 

 early as 1807, Benedict Prevost gave 4 an account of the method 

 by which he prevented the germination of the spores of a fun- 

 gous disease commonly known as " Carie," or " Charbon " 

 (smut), of corn. His statement regarding the result of his 

 experiments is as follows : " The amount of sulphate of copper 

 really necessary to give to water the power of preventing the 

 germination of the spores in a low temperature does not 

 amount to ^oW of its weight, and TT ^ retards germina- 

 tion." Thus a discovery of immense practical importance has 

 long remained hidden and unappreciated, and it is not impos- 

 sible that other information equally valuable is at present 

 neglected in a similar manner. 



The first general statement in regard to the value of chemi- 

 cal compounds for the destruction of grape mildew seems to 

 have been made by Millardet. 5 He says : " Recent observa- 



1 Comptes Rendus de VAcademie des Sciences, 1877, Nov. 12. 



* Jour. d'Ag. Prat. 1881, July 7, 20. 



8 By an 8 per cent solution is meant a solution which contains 8 parts by 

 weight of the solid dissolved in 100 parts of the liquid. 



4 " Memoire sur la cause immediate de la Carie ou Charbon des bles." Montau- 

 ban, 1807. 



6 Zeitechrift in Wein-, Obnt-, und Garteribau fur Elsass-Lothringen, 18S3, 

 March 1 and 15. 



