BLAKESLEE. — SEXUAL- REPRODUCTION IN THE MUCORINEAE. 257 



seventy-one (+) and six (— ), and of these latter, four came from the 

 suspensors of individual zygospores in cases where both had germinated. 



A number of spontaneous infections of Rhizopus in laboratory cultures 

 were tested at this time and found to be (+) in character, a fact which 

 maie it seem possible that the (— ) strain was exotic, and, being carried 

 on the nut shells, either by handling or by infection in the paste cult- 

 ures, became mingled with the (+) strain apparently predominant in the 

 laboratory. Through the kind assistance of Mr. V. B. Swett it is jiossi- 

 ble to state that in all probability the two strains are present side by side 

 on the nuts as bought. Several spontaneous cultures of bread and of a 

 number of different vegetables were started by him at the writer's sug- 

 gestion at the same time with a culture of nut shells on moist bread. 

 The failure of Khizopus to develop on the other spontaneous cultures 

 indicated the comparative rarity of spores of this fungus in the air of the 

 apartments and rendered probable that its luxuriant growth on the nut 

 bread culture came entirely from spores carried on the nut shells. The 

 zygospores which here appeared were the starting point of Culture D, 

 which was separated by taking transfers from two zygospores both sus- 

 pensors of which had germinated so that two transfers belonged to each 

 strain. The strains obtained produced zygospores when contrasted with 

 the proper strains of Culture A. 



Culture E was obtained as already mentioned (p. 233) from an infec- 

 tion of a mixture of vegetables at the Botanic Gardens. Pure sporan- 

 gial transfers were made from a carrot, an onion and a sweet potato, and 

 in addition young zygospores from cultures obtained from this mixed 

 growth were laid on nutrient agar and mycelial transfers E^ to Eg were 

 taken from germinations of their suspensors. Eg was apj^arently an im- 

 pure transfer as seen by its giving zygospores with both A(-f-) and 

 A( — ). That zygospores did not show in the tube culture made from 



TABLE VL CcLTURE E. 



