28 



SOME FUNGOUS DISEASES OF ECONOMIC IMPORTANCE. 



VITALITY OF MICROSPORES AND MACROSPORES. 



A series of experiments was made to determine the relative vitality 

 of the microspores and macrospores of Thielaviopsis. The method 

 was to simultaneously expose the two different kinds of spores sus- 

 pended in distilled water to the action of the formaldehyde gas in 

 various quantities and different time limits. At the conclusion of 

 each experiment transfers were made to fresh culture media. Nega- 

 tive results as to growth were obtained in all the experiments with 

 quantities of formalin exceeding 1,000 c. c. per 1,000 cubic feet of 

 air space. Referring to the following tables it will be observed that 

 the macrospores survived the fifteen and thirty minute treatment, 

 while the microspores produced no growth. 



Experiment No. 22. 



750 c. c. formalin per 1,000 cubic feet of air space. 

 Temperature before mixing reagents, 68° F. 



Thielaviopsis spores suspended in water. 



Initial growth of 

 fungus. 



Micro- 

 spores. 



Macro- 

 spores. 



Check; fungus not exposed to formaldehyde gas 



Fungus exposed 15 minutes 



Fungus exposed 30 minutes 



Fungus exposed 60 minutes 



Hours. 

 22 

 

 

 



Hours. 



22 



96 



120 







Experiment No. 23. 



850 c. c. formalin per 1,000 cubic feet of air space. 

 Temperature before mixing reagents, 68° F. 



Thielaviopsis spores suspended in water. 



Initial growth of 

 fungus. 



Micro- 

 spores. 



Check; fungus not exposed to formaldehyde gas 



Fungus exposed 15 minutes 



Fungus exposed 30 minutes 



Fungus exposed (30 minutes 



Hours. 

 22 





 

 



Macro- 

 spores. 



Hours. 



22 



190 



200 







Experiment No. 2 '/. 

 950 c. c. formalin per 1,000 cubic feet of air space. 

 Temperature before mixing reagents, 78° F. 



Thielaviopsis spores suspended in water. 



Initial growth of 

 fungus. 



Micro- 

 spores. 



Macro- 

 spores. 



Check; fungus not exposed to formaldehyde gas 



Fungus exposed 15 minutes " 



Fungus exposed 30 minutes 



Fungus exposed c,o minutes 



171 



Hours. 

 22 

 

 

 



Hour-. 



22 







113 







