INOCULATION EXPERIMENTS. 



31 



Experiment No. SO. 



1.200 c. c. formalin per 1.000 cubic feet of air space. 

 Temperature before mixing reagents, 76' F. 



Thielaviopsison the fruit. 



Initial Vigorous 

 growth of growth of 

 fungus. fungus. 



Per cent 



of fungus 



which 



grew. 



Checks; transfers of the fungus before fumigation 



Transfers of the fungus after 60 minutes of fumigation 



Hours. Hours. 

 26 42 



-:o 131 



100 

 60 







After ninety-six hours the fungus was well developed from all 

 centers of inoculation in non fumigated fruit, while no growth of the 

 fungus was apparent in the fumigated fruit. At the expiration of 

 one hundred and twenty hours the nonfumigated material was badly 

 decayed, although the fumigated fruit was still firm and in market- 

 able condition. 



Plate IV shows a typical set of fruit pertaining to the preceding 

 experiment. A. B< and C represent the check, inoculated and fumi- 

 gated, and inoculated and nonfumigated fruit, respectively, taken 

 seventy-two hours after fumigation. C shows three separate centers 

 of infection, while B similarly inoculated but fumigated has resisted 

 the disease. The condition of C is still more strikingly represented 

 in Plate VIII. figure 1. 



Experiment No. 31. 



1,250 c. c. formalin per 1,000 cubic feet of air space. 

 Temperature before mixing reagents, 76 s F. 



Thielaviopsis on the fruit. 



Initial 

 growth of 

 fungus. 



6 grew. 



Checks; transfers of the fungus before fumigation 



Hours. 

 43 

 ISO 



Hours. 

 80 

 200 



100 00 



Transfers of the fungus after 60 minutes of fumigation 



16.66 



The nonfumigated fruit was badly decayed after one hundred and 

 twenty hours. The fumigated fruit remained firm and in marketable 

 condition. 



Plate V is a reproduction of a photograph taken of cultures from 

 the fruit before and after fumigation with 1,250 c. c. of formalin per 

 1.000 cubic feet of air space. The difference between the checks and 

 transfers shows very strikingly the effect of the formaldehyde gas on 

 the fungus. 



341 14— Bui. 171—10 3 



