TOXICITY OF HEAVY METALS 67 



TOXICITY OF SALT COMBINATIONS 



Calcium, Magnesium and Potassium. 



It requires a relatively high concentration of calcium, magnesium or 

 potassium nitrate to inhibit the germination of these spores. With 

 Ca(NO 3 ) 2 normal germination was found in the 0.5111 solution and 

 swollen tubes were abundant in o.6m. At a concentration of o./m, how- 

 ever, none of the spores germinated in any of the four series of duplicate 

 cultures which were carried out. The concentration of this salt which 

 just prevents germination appears, therefore, to lie between o.6m and 

 o./m. Magnesium nitrate is similar to that of calcium in its effect. With 

 this salt the spores germinated normally at a concentration of 0.4111, and 

 local swellings of the spore wall and swollen tubes were produced in 0.5111 

 solution, while no germination was evident when a o.6m concentration was 

 employed. The concentration at which Mg(NO 3 ) 2 just inhibited germin- 

 ation thus seems to lie between o.5m and o.6m. In solutions of KNO 3 

 the spores germinated normally with a concentration of 0.9111 and formed 

 local swellings of the spore wall with molecular concentration. As the 

 latter was the highest concentration here used, the 

 point at which KXCX inhibits germination was not 

 determined. 



The exceedingly high .concentrations of these salts, 

 which were found necessary to inhibit germination, 

 made it seem possible that they might be without toxic 

 effect upon the spores ; the inhibition of germination 



which was observed in high concentrations might have 



.-..-, . in? spores from i.6m 



been the result of the high osmotic pressure exerted sucrose solution, x 



by the medium. To obtain evidence on this point the 550. 

 germination of the spores was tested in cane sugar 



solution at various concentrations. A o.2m stock solution was prepared 

 from granulated sugar which had been previously pulverized and desic- 

 cated ; the different concentrations used in the cultures were prepared from 

 this. The spores germinated normally in concentrations of cane sugar 

 up to and including i-4m, considerable germination in the form of local 

 swellings (shown in fig. i) was found in the i.6m solution, and no germina- 

 tion occurred with i.8m concentration. The concentration of cane sugar 

 which just inhibits germination lies then between i.6m and i.8m. 



It will be observed that a i.6m solution of sucrose has about the same 

 effect upon the germination of these Gloeosporium spores as do o.6m, 0.5111 

 and molecular solutions of calcium, magnesium and potassium nitrates 



