THE FUNGI 



263 



Suspensors 



r 



TJie germination of the spores takes place as follows : When 

 they come to rest on a proper nourishing medium, the spores 

 absorb water, the outer coat ruptures, and the delicate inner coat 

 expands into a tubular hypha, into which the protoplasm of the 

 spore flows (Fig. 141, d and e). As the hypha elongates it ab- 

 sorbs new nutriment, by means of which it grows and branches 

 to form a new plant body, or mycelium. Usually several spores 

 germinate in close proximity, and the hyphse produced by the 

 different spores commingle to make one fluffy, 

 white mycelium characteristic of the black molds. 



Sexual reproduction. Under special conditions 

 two hyphae, belong- 

 ing to separate my- 

 celia of different 

 kinds, or strains, 

 may conjugate and 

 produce a zygote. 

 Each hypha sends 

 out a fertile hyphal 

 branch, or bud, 

 called a suspensor. 

 The two branches 

 grow toward each 

 other in much the 

 same way as the 

 conjugating tubes 



do in Spirogyra, and each suspensor cell then cuts off at its 

 apex a cell which corresponds to a gametangium (Fig. 142). 

 The two end cells, or gametangia, of the approaching suspensors 

 meet, and the protoplasts (gametes) unite after the solution and 

 disappearance of the cell walls of the two gametangia at the point 

 of contact. The zygote cell thus formed enlarges and forms the 

 usual heavy protective walls of a zygote. After a period of rest 

 this zygote may germinate and produce a new mycelium (<?), from 

 which sporangia and asexual spores will be formed as described 

 above. Although the sexual reproduction of Rhizopus and Spi- 

 rogyra are similar, the two plants have no near relationship. 



A' - - 

 Gametes 



Suspensors 

 b 



FIG. 142. Sexual reproduction in Rhizopus 



a, formation of the suspensors and gametangia ; b, forma- 

 tion of the zygote ; c, germination of the zygote to form 

 a new sporangium 



