THS INFLUENCE OF CALCIUM, MAGNESIUlf AND POTASSIUI.I NITRATES 

 UPOK THE TOXICITY OF CERTAIN HEAYY l.STALS 

 TO'ffARD FUNGUS SPORES. 



DISSERTATION 

 Submitted to the Board of L'niversity Studies of 

 the Johns Hopkins University in conformity 

 with the requirements for the degree 

 of Doctor of Philosophy 



by 

 LON A. HAWKINS 



Baltimore, June, 1913. 



