24 TECHNICAL BULLETIN 149, U. S. DEFT. OP AGEICULTTJEE 



higher plants, and among the mushrooms there are numerous species 

 whose toxins have caused the deaths of great numbers of mushropm 

 eaters. Although numerous species of the Hyphomycetes are active 

 parasites of other fungi, higher plants, and animals, very little has 

 been done to demonstrate the nature of the toxic substances elab- 

 orated by these organisms. 



In the progress of some plant diseases caused by fungi the cells 

 of the host are killed or altered far in advance of the developing 

 mycelium of the parasite. This is particularly true among the rusts 

 where zones of dead cells may surround the infected spot. The 

 death of the cells of the host not in direct contact with the fun,gus 

 can probably be attributed to toxic products of the parasite. 



A few reports oi toxic substances produced by filamentous fungi 

 are on record. In 1906 Paladino-Blandini {W, f. 608) prepared an 

 alcoholic precipitate from the mycelium of Rhizofus nigricans which 

 was toxic to rabbits when injected intravenously. In 1915 Blakes- 

 lee and Gortner {3) published a more complete study of this toxin 

 and its action upon rabbits. In earlier experiments by these two 

 investigators {11), results with rabbits were negative when the 

 fungus was administered by feeding in large doses. (Such an alco- 

 holic extract would be a protein, and its nontoxic nature when fed 

 can be explained by its digestion to nonpoisonous compounds before 

 absorption.) In 1896 Gosio (i^), working with a species of Peni- 

 cillium, found that the culture medium gave phenol reactions. When 

 injected into rabbits and rats, phenol poisoning resulted. In the 

 study of maize deterioration, Alsberg and Black (i, p. 13, Jf3) iso- 

 lated a characteristic phenolic substance from PenicilliuTn fubervHum 

 and P stoloniferu<n%. This substance could only be isolated from 

 the medium. Turesson {26) as a result of his work on the toxicity 

 of fungi concludes that it is of wide occurrence in fungi. 



To determine whether or not such a toxic substance injurious to 

 living bees is produced by these fun,gi experiments Avere begun with 

 two pathogenic organisms, AspergUlus flavios Ao5c (Thom collec- 

 tion) and A fumigatus, isolated from an infected worker bee. 



Direct injection into the blood of bees was considered impractic- 

 able; consequently feeding experiments were adapted as a test for 

 the toxicant. Food prepared by the addition of honey to the medium 

 in which these Aspergilli had been grown and to juices pressed from 

 mycelium was fed to caged bees. When the unheated medium or 

 fungous juice from cultures was used it was necessary to filter it, 

 using the best grade of filter paper, to eliminated spores of the patho- 

 genic organisms. This was partially accomplished only with Asf&r- 

 gillus flavus. A. fumigatus was not used after the first attempt on 

 account of the small size of the spores. Although the death rate 

 among the bees fed with medium in which cultures had matured aver- 

 aged higher than among the checks which were fed freshly prepared 

 medium, the method was discarded because the death rate among the 

 checks, due to salts, was higher than normal. When bees were fed 

 with the fluids pressed from' mycelium, or with the wash water from 

 the mycelium, the death rate remained about normal. It appeared, 

 therefore, that if a toxic substance is produced, it must be sought in 

 the medium rather than in the mycelium of the fungus. 



