SUMMARY. 35 



experiments were performed, and the humidity would be considerably 

 higher than 38 per cent. 



The macrospores exhibited much greater resistance to the action of 

 the gas than the microspores, and a dormant period did not precede 

 their germination. 



The degree of moisture present on the fruit at the conclusion of 

 the fumigating process was not excessive, and although the odor of 

 formaldehyde was quite apparent it was soon dissipated. The gas 

 produced no immediate change in the consistency of the fruit, but a 

 flight change was noted at the termination of four days. Whether 

 this was an after effect of the gas is difficult to determine without 

 a large quantity of fruit for comparison. The fruit did undergo 

 an alteration in color, but it was not striking, and whether the gas 

 would produce a similar effect in freshly picked fruit is yet to be 

 determined. 



The effect of the gas on cultures of the fungus and the fungus 

 present on the fruit sprayed with spores or with spores introduced 

 into cavities or the tissue was found to be constant. It is not claimed 

 that the development of the fungus can be arrested if it has pene- 

 trated very far into the tissues of the fruit, but the fungus was killed 

 when inserted in the fruit to a depth of one-half an inch. The 

 development of the fungus on the fruit sprayed with spores and 

 that inoculated by incisions was as great, if not greater, than it would 

 be when the fruit is brought to the packing houses, since the 

 danger is largely due to superficially adherent spores. Although 

 unsubstantiated by field and packing-house observations, it is fair 

 to assume that formaldehyde gas is an effective agent in controlling 

 pineapple rot. 



SUMMARY. 



Formaldehyde gas is an efficient means of controlling Tkiela''io{>*<* 

 paradoxa ( De Seyn.) V. Hohn. 



The macrospores exhibited a much greater resistance to the action 

 of the gas than the microspores. 



There was no marked anatomical change in the appearance of the 

 fungus after fumigation, and it is believed that the effect is of a 

 chemical rather than of a physical nature. 



Even small quantities of the gas exert a retarding action upon the 

 initial growth of the fungus. 



The quantity of gas fatal to the fungus is generated from formalin 

 in quantities ranging from 1.200 to 1.300 c. c. per 1.000 cubic feet of 

 air space under physical conditions comparable to those used in the 

 experiments described in this paper. 



171 



