52 



S. E. A. McCallan 



TABLE 5. Percentage Germination of Sclerotinia Americana Conidia in Calcium- 



Sulfate Solutions 

 (Spores 5 days old) 



The toxicity of calcium carbonate was tested, using the material as a 

 dust. Three tests were made, the slides being dusted in the usual manner. 

 On the addition of the aqueous spore suspension, a saturated solution of 

 the calcium carbonate would presumably result and be present together 

 with the very great excess of solid dust particles. The results are shown 

 in table 6. 



TABLE 6. 



Percentage Germination of Sclerotinia Americana Conidia on Slides 

 Dusted with C. P. Calcium Carbonate 



These tests show that a clear saturated solution of calcium hydroxide 

 in water is decidedly toxic toward conidia of Sclerotinia americana. Nor- 

 mal germination is obtained only when the solution has been diluted to 

 6 per cent of saturation. 



Solutions of calcium sulfate also are toxic. They are, however, ap- 

 proximately only one-sixth as toxic as similar concentrations of calcium- 



