CHAPTER IV 



EFFECT OF ZINC COMPOUNDS 



I. PRESENCE OF ZINC IN PLANTS. 



THE presence of zinc in the ash of certain plants has been recognised 

 for many years, especially in so far as the vegetation of soils containing 

 much zinc is concerned. Risse, before 1865, stated that most plants 

 when grown on such soils prove to contain greater or less quantities of 

 zinc oxide. He states that the soil at Altenberg, near Aachen, is very 

 rich in zinc, which rises as high as 20 / in places. The flora of the soil 

 is very diversified and zinc has been determined qualitatively in most 

 and quantitatively in some of the plants. Viola tricolor and Thlaspi 

 alpestre are most characteristic under such circumstances, both showing 

 such constant habit changes that they resemble new species, while other 

 plants such as Armeria vulgaris and Silene inflata are peculiarly 

 luxuriant. Risse's figures of the zinc content of these four plants 

 may prove of interest. The figures are based on the dry weights, 

 air dried. 



Thlaspi alpestre, var. calaminaria. 



Root 6-28 % ash, 0167 % ZnO, 1'66 % ZnO in ash. 



Stem H'75% 0-385% 3'28% 



Leaves 11'45 % 1'50% 1312% 



Flowers 8'49% 0'275% 3'24 % 



Viola tricolor. 



Root 5-59 % ash, 0'085 % ZnO, 1-52 % ZnO in ash. 



Stern 10-55% 0-065% 0-62% 



Leaves 9'42% 0-110% 116% 



Flowers 7'66% 0-075 % 0'98 % 



