Rr.AKESLEE. SEXUAL REPRODUCTION IN TME MUCORINEAi:. 271 



were reversed. Accordingly to test the matter further and to determine 

 what if any diflference iu growth exists between the (+) and ( — ) 

 strains, on March 23 the (+) and ( — ) strains of the cultures A to H 

 were mutually contrasted in crystallizing dishes of flour paste, and in 

 addition contrasts were made between (+) and (— ) strains obtained 

 from Worcester, Mass., and Nancy, France. All of these contrasts 

 produced zygospores, but although in some tlie sporangial growth was 

 slightly higher on one side of the dish, this difference had no relation to 

 the places of inoculation, and in none of the cultures could any difference 

 be observed in the growtli of the two strains. Tlie only difference, there- 

 fore, by which at present tlie .strains of Rliizopus can be distinguished 

 lies in their sexual action when grown in contact. 



MUCOR MUCEDO. 



During the past few years the writer has been conducting numerous 

 gross cultures of coprophilous fungi in several of which zygospores have 

 been found which from their general appearance and from the sporangial 

 growth with which they were associated have been referred to that sub- 

 division of the genus Mucor of which J/. Mncedo may be taken as the 

 type. Although it seems certain that the forms thus associated repre- 

 sent more than a single sjiecies, the one which forms the basis of the 

 present discussion appears to agree with Brefeld's ('72) description, and 

 therefore may be assumed to be the typical M. Mncedo. It has been 

 generally impossible, when zygospores have been found, to continue their 

 formation in tube cultures by either sporangial or mycelial transfers. 



In January, 1903, however, zygospores of this type form were found 

 growing spontaneously on a certain gross dung culture in so compara- 

 tively pure a condition that it was possible by making mycelial transfers 

 to hard agar to free the growth from the associated bacteria and to 

 obtain a pure culture of this Mucor with an abundant production of its 

 zygospores. The same difficulty that has already been mentioned of 

 the early cultures of Rhizopus was here experienced in inducing zygo- 

 spore formation from a sporangial inoculation. If a mass of the 

 mycelium ])roducing zygospores was transferred to nutrient agar, 

 zygospores formed in a dense mass around the point of inoculation, but 

 their numbers soon diminished as the mycelium widened its growth. 

 Transfers from single sporangia never produced zygospores and zygo- 

 sporic cultures were therefore kept running by mass transfers of the 

 mycelium. Repeated attempts to produce zygospores from mixed 

 sporangial transfers demonstrated the fact, however, that while mixed 



