EFFECT OF FUMIGATION. 33 



EXPERIMENTS WITH ERUIT SPRAYED WITH SPORES OE 

 THIELAVIOPSIS. 



Experiments corresponding with the inoculation work in number 

 and in the quantities of formaldehyde gas used were made with fruit 

 sprayed with spores of Thielaviopsis. After the fruit was sprayed it 

 was kept in a warm. damp, and dark atmosphere for forty-eight 

 hours previous to fumigation. The fungus did not develop on the 

 fumigated fruit in a single case, though the nonfumigated fruit be- 

 came diseased in every instance. 



Plate VII shows what the effect of fumigation would be in pre- 

 venting the infection of fruit by superficial spores. The photograph 

 was taken one hundred and twenty hours after the fruit was sprayed 

 with spores, or seventy-two hours after it was fumigated with 1.200 

 c. c. of formalin per 1.000 cubic feet of air space. The differences 

 between check, fumigated, and nonfumigated fruits are very ap- 

 parent. The development of the fungus in a sprayed and nonfumi- 

 gated fruit is more strikingly shown in Plate VIII. figure 2. 



EEEECT OE FUMIGATION ON THE ERUIT. 



The fruit used in these experiments was obtained from different 

 sources and comprised several varieties. Observation- of the varietal 

 peculiarities in the presence of the formaldehyde gas were not suf- 

 ficiently extensive to be included in this paper. 



An effort was made to determine the effect of fumigation on the 

 fruit. Immature and mature pineapples were subjected in each 

 experiment, after the completion of which they were kept indefinitely 

 to observe any change which might take place in their appearance. 

 It was found that the use of large quantities of formalin, as "2.600 

 c. c. per 1.000 cubic feet of air space, produced no immediate altera- 

 tion. In quantities from 1.000 c. c. to 1.300 c. c. the fruit suffered a 

 slight change in color, becoming somewhat brown. Besides this 

 change in color there was a slight shrinkage and a loss of turgidity. 

 Xone of these effects were remarkably conspicuous, and it seems prob- 

 able that they may be controlled. There was no opportunity for 

 observing the effect of fumigation on freshly pulled fruit. 



In the experiments a small amount of moisture condensed on the 

 fruit during the fumigating process. Quantitative determinations 

 were not made of this amount, but it was so small that it could not be 

 determined by means of delicate torsion balances by finding the dif- 

 ference in the weight of the fruit before fumigation and after sub- 

 jection to formaldehyde gas. The moisture, together with the odor 

 of formalin, which was very marked on the fruit immediately after 

 it was taken from the fumigating box. quickly disappeared. The 

 following table gives the increase in moisture in the atmosphere due 

 to the liberation of the different quantities of the gas. 



171 



