.MORPHOLOGY OF MOLDS 29 



reproduction, fo-filr Injplui. The term mycelium is ap- 

 plied to the entire mass of growth resulting from a single 

 spore. 



The filaments may be divided by cross-walls, or septa, or 

 they may not be so divided. In the septate mycelium each 

 cell contains a nucleus. In the non-septate mycelium, nu- 

 clei occur at intervals along the thread in the protoplasm. 

 Therefore even the non-septate molds are to be classed as 

 mnlticellular. The threads branch at frequent intervals. 

 The microscopic appearance of the mycelium is that of a 

 mass of tangled filaments. The filaments are not usually all 

 in contact with the food, but rise into the air to some extent, 

 giving to the typical mold a fluffy appearance. The hyphaj 

 are usually colorless. 



Reproduction is by the formation of spores, which are 

 produced in enormous numbers. In some species both 

 s.'.xual and asexual spores are produced. The former are 

 of small practical importance and will not be treated. The 

 asexual spores are most often borne on hyphae that rise into 

 the air and are thus out of contact with the moist food ma- 

 terial, a fact of importance when their distribution is con- 

 sidered. The manner of production, their size, shape and 

 color, are the most important characteristics used in the 

 classification of molds. The spores are often colored, 

 brown, black, and green being the most common. 



In a number of the more important groups of molds,-the 

 spores are produced on the ends of the filaments. Such fil- 

 aments are called conidiophores, and the spores conidia. In 

 otln-rs they are formed in closed sacs, called sporangia, the 

 filament bearing the sac being termed a sporangiaphore. 

 The latter type of spore formation is limited to the non- 

 septate molds. The mature sporangium usually bursts, 

 and the numerous sporangia spores are set free. The spor- 

 ingium is quite comparable to the ordinary puff-ball. Some 



