10 BULLETIN 127, U. S. DEPARTMENT OF AGRICULTURE. 



their power of germination. Several hundred cultures were made 

 during this series of experiments, and no growth was produced from 

 cultures after a period of IS months. It should be stated, however, 

 that the cultures were kept in a dry place and were consequently 

 thoroughly dried out at the termination of 18 months. That the 

 organism retains its vitality for such a period and on an artificial 

 medium demonstrates its dangerous nature. The probability is 

 strong that in the mushroom house, under more favorable conditions 

 of humidity and temperature, it would retain its power of germina- 

 tion much longer. 



Field observations. — The writer's opportunity to study the vitality 

 of Mycogone in the beds of different mushroom houses has covered a 

 period of about three years. One case for observation was that of 

 a new house in which earth was mixed with manure from a badly 

 infected house, which manure had been exposed to the weather for 

 five years. This house produced a splendid crop of mushrooms, 

 which indicates that the fungus exposed to the weather had not 

 retained its vitality at the close of this period. A case in which the 

 fungus persisted for three years is cited by Costantin. Two caves were 

 held under observation; one was new, while the second had been 

 used for mushroom cultivation for over 30 years, although the culture 

 had not been continuous. This second cave was idle for three years 

 before being employed for this experiment. The yield of the new 

 cave exceeded that of the second, and the presence of the disease in 

 the first was negligible, while in the second it was considerable. 

 The conditions and attention in the two caves were practically the 

 same, and, while the report does not mention what precautions were 

 observed to prevent infection of the new beds, the result would indi- 

 cate that the spores in the abandoned cave had retained their vitality 

 for at least three years. 



CULTURAL STUDIES TO DETERMINE A MEANS OF CONTROL. 



Many hundreds of cultures of Mycogone were made during the 

 course of the present investigation, for the purpose of studying the 

 development and habit of the fungus and observing the direct effect 

 of fungicides and disinfectants upon the organism. It was found 

 that the fungus could be cultivated upon numerous different media, 

 but as corn meal in flasks and corn-meal agar proved very congenial 

 media they were employed in most of the experiments. The fungus 

 grew rapidly, producing vigorous cultures, and practically no diffi- 

 culty was experienced from contaminations even when fresh cultures 

 were made directly from diseased mushrooms on which spores of 

 various fungi were doubtless present. Figure 3 shows a photograph 

 of one of the cultures, all of which exhibited a similar vigorous growth. 

 In the early stages the cultures of the fungus were white, soon becom- 



