4o8 



General Botany 



upright hjrphae which terminate above in sporangia. Just be- 

 neath each cluster of sporangial hyphae a much-branched 



Columella - 



Fig. 250. Bread mold {Rhizo pus) : ^ , showing general habit of growth ; 5, sporangium 

 enlarged ; C, D, E, and F, stages in the formation of a zygospore. 



rhizoid grows downward into the bread, affording anchorage and 

 a food- and water-absorbing surface. 



Under favorable moisture and temperature conditions the my- 

 celium developed from a single spore may entirely surround 

 a slice of bread with a white, fluffy, cottony growth, dotted with 

 countless sporangia filled with black spores. 



The bread mold may also reproduce in another way. When 

 filaments from different strains of the fungus grow in contact, 

 they may each form small, lateral, club-shaped branches. 

 Then each of the branches is cut off by a wall near the 

 inner end, forming a cell, the contents of which act as a 

 gamete. Finally, the cell wall between the two gametes unite, 

 forming a zygote or sexual spore. A heavy, rough black wall 

 forms around it and it becomes a resting spore. Under favorable 

 conditions, after a period of time, it germinates and produces a 

 new mycelium with sporangia and asexual spores. The bread 

 mold derives its water and food from the moist bread through 



