SPORE EXPULSION AMONG PHYCOMYCETES 



185 



The recoil of the basal wall of the conidium against the impinging 

 apical wall of the conidiophore acts as a spring, and in conse- 

 quence the conidium is violently pushed into space. Its passage 

 through the field, when material in the humid atmosphere of a 

 Van Tieghem cell is viewed with a microscope, appears like a 



Fig. 31. Schematic diagrams showing stages in sporangial (conidial) dis- 

 charge in Basidiobolus ranarum. (After Ingold.) A. Zone of weakness 

 apparent near base of subsporangial swelling. B. Sporangium liberated from 

 upper part of subsporangium. C. Sporangium freed, but with empty, 

 thimble-like subsporangium attached. D. Germination of conidium with 

 secondary discharge in progress, a repetitional phenomenon. 



streak of light. The roughened ring, marking where the conidium 

 was torn from its attachment of the conidiophore, can also be 

 observed readily, the end of the conidium being normally everted 

 on lodging. 



The accounts by Levisohn (1927) and Ingold (1934) of the 

 mechanism in Basidiobolus ranarum indicate that it is quite dif- 

 ferent from that in Entomophthora, being more nearly like that 

 in Pilobolus. Basidiobolus ranarum occurs in frog excreta and 

 can readily be made to develop and discharge its conidia on ab- 



