THE FUNGI 233 



either germinate into a new mycelium or give rise at 

 once to sporangia. 



b. Sexual 



More important for us is the sexual reproduction, 

 which in Pilobolus and many of its relatives takes place 

 but rarely, though in some other members of the group it 

 is the most frequent means of propagation. Sexual organs 

 are only formed in Pilobolus when some cause hinders 

 the development of the sporangia. It has been found 

 that conjugation can be induced by infecting the aerial 

 hyphae with a parasitic Fungus (which happens to be a 

 relative, for several members of the group prey upon 

 their own family). The parasite hinders the formation 

 of the asexual spores, and the plant is thus led to adopt 

 the other method of propagation, which results in the 

 formation of resting-spores capable of waiting until the 

 bad times are over. 



When conjugation is about to take place, two neigh- 

 bouring branches of the mycelium enlarge, and become 

 club-shaped (Fig. 96, G and H). The swollen portions 

 grow upright, and lay themselves together side by side, 

 accumulating at the same time a large quantity of proto- 

 plasm in their interior. The ends of the conjugating 

 hyphae are next cut off by cell-walls (Fig. 96, J). The 

 terminal parts thus separated, which are the richest in 

 protoplasm, come into close contact, and the cell-walls 

 separating them are absorbed. The protoplasm of the 

 cells now runs together into one mass, and the two cells 

 completely fuse into a single zygospore, which rests upon 

 the two enlarged hyphse, called the suspensors (Fig. 

 96, K, z). The zygospore grows to a relatively great 

 size, surrounds itself with a very tough and thick cell- 



