FUNGI, BLACK MOLD 



25 1 



protoplasm is coarsely granular and shows numerous vacuoles of 

 varying size (fig. 210). The protoplasm shows streaming move- 

 ments. It flows along in a thread-like stream, or in other cases 

 there may be smaller currents up and down the thread. There 

 are large numbers of nuclei in the protoplasm, but they cannot 

 be demonstrated without careful treatment according to certain 

 technical methods. Cross walls appear where reproductive 

 bodies or organs are formed, and rarely here and there in old 

 mycelia 



405. Sexual reproduction. Sexual reproduction takes place 

 by conjugation. This occurs between two threads or branches of 



Fig. 211. 

 Rhizopus nigricans. Different stages in conjugation of + and strains to form zygospores. 



mycelium which are of an opposite sex nature. One cannot dis- 

 tinguish between male and female according to the size and appear- 

 ance of the conjugating branch, though sometimes at a later stage 

 one becomes much larger than the other. The branches meet 

 at their ends, and each swells into a club-shaped body. A cross 

 wall now cuts off a body of protoplasm in the end of each branch. 



