The Effect upon the Soil. 235 



The benefits derived have not yet been fully determined. It 

 has been estimated that the germination of spores of certain 

 fungi may be prevented by solutions of lime containing 1 part 

 to 10,000 of the liquid ; or iron sulphate, 1 part to 100,000 of 

 water ; or copper sulphate, 1 part to 10.000,000 of water. 1 This 

 readily explains the energetic action of the copper compounds, 

 and why such small amounts may be applied to advantage. 



For further information concerning the action of copper 

 compounds when applied to plants, consult R. Otto, "Unter- 

 suchungen iiber das Verhalten der Pflanzenwurzeln gegen Kup- 

 ^ersalzlb'sungen" (Zeitschrift fur Pflanzenkrankheiten, Bd. iii. 

 J.893, Heft 6). The plants studied in these investigations 

 were Phaseolus vulgaris, Zea Mays, Pisum sativum. It was 

 found that " copper exercises a poisonous influence upon the 

 plants, it interferes with the development of the roots and 

 lessens the activity of the functions of the plant, or kills the 

 latter outright, when the roots of the plants are growing in 

 more or less concentrated solutions of copper sulphate." It was 

 also found that practically no copper was absorbed by the roots, 

 and the parts above ground were entirely free from the metal. 

 See review in Botamsches Centralblatt, 1893, Vol. 55, 340-342. 



See also, A. Tschirch, "Das Kupfer vom Standpunkte der ge- 

 richtlichen Chemie, Toxicologie, und Hygiene. Mit besonderer 

 Beriicksichtigung der Reverdissage der Conserven und der 

 Kupferung des Weins und der Kartoffeln." Stuttgart (F. Enke), 

 1893. The entire question of the use of copper compounds 

 upon cultivated plants is thoroughly discussed by the author. 

 In general his conclusion is, " to remove all copper from articles 

 of diet means forbidding the plant to absorb it from the soil, 

 and also considering as injurious to health the use of bread and 

 chocolate." See Botanisclies Cenlralblatt, 1893, Vol. 55, 170-175, 

 for a detailed review of the work. 



IV. UPON THE SOIL. 



Doubts have been very frequently expressed as to the final 

 outcome of the continual addition of insecticides and fungicides 

 to the soil, it being supposed that the roots of the plants as 

 well as the soil itself would eventually suffer. Scientific inves- 



i Millardet et Gayon, Jour. cVAg. Prat. 1885, Nov. 12, 707. 



