Effect of Zinc Compounds 



41 



in advance of that of the shoots, probably on account ofjhe^ontact of 

 the, roots with the poison. In the greater strengths of such poisons as 

 zinc and copper sulphate root growth is checked from the outset, but 

 usually a very little shoot growth is made, and one frequently obtains 

 ridiculous little plants about an inch high bearing unhappy and diminu- 

 tive flowers, which are occasionally replaced by equally unhappy and 

 miniature fruits. The same thing has also been noticed when un- 

 successful attempts have been made to introduce spinach as a test plant 

 for water cultures. 



gm. 

 1-8 



1-0 



•8 



•6 



200 100 20 



4. 2 I -4 



1 = 1:1,000,000 



■05 



Fig. 8. Curve showing the mean values of the dry weights of nine series of pea plants 

 grown in the presence of anhydrous zinc sulphate and nutrient salts. (May 18th — 

 June 28th, 1910.) 



(c) Effect of zinc compounds on plant growth when they are present 

 in soils. 



As soon as the presence of zinc in members of the vegetable kingdom 

 was established the question arose as to its. effect upon both the plant 

 and the soil. 



Gorup-Besanez (1863) grew plants in soil with which 30 grams of 

 metallic poisons such as CuSOi, ZnSOt, HgO, were intimately mixed 

 with 30-7 litres ("cubik Decimeter") of soil'. On analysing the ash of 

 Secale cereale, Polygonwm Fagopyrum, and Pisum sativum after six 

 months growth he failed to detect the presence of zinc in any one of 

 the three. As the results varied with different poisons on different 

 plants he concluded that the absorption capacity of the various kinds of 



1 This is equivalent to about -1 % °^ poison. 



