42 VETERINARY BACTERIOLOGY 



cell, although the statement is often made that the entire mold 

 filament in the non-septate type is a single cell. 



Reproduction of Molds. It is impracticable to go into detail 

 concerning the reproduction of molds. Spores of many different 

 types are produced (Fig. 22), sometimes three or four kinds by 

 a single species. The spores exhibit every conceivable shape and 

 coloring, are sometimes unicellular, at other times multiseptate. 

 Hundreds of genera and thousands of species are known. The 

 names applied to the different parts of the molds concerned in 

 reproduction and the manner in which the spores are borne in 

 some of the commoner molds may, however, be briefly discussed. 



Molds may be divided, for convenience, into those which 

 bear the spores enclosed in a spore case or sporangium and those 

 in which they are not so inclosed. This sporangium is commonly 



Fig. 22. Types of mold spores. 



borne at the tip of a hyphal thread differentiated for the pur- 

 pose, called a sporangiophore. Spores not produced inside of 

 a sporangium and not the result of fertilization (i. e., asexual 

 spores) are termed conidia (sing, conidiwri). Conidia are usually 

 developed at the tip of specialized branches called conidiophores. 

 Sometimes they are formed by the breaking up of the mycelial 

 threads or hyphae, and are then called o'idia (sing, o'idium), 

 in other cases they develop within the hyphae and are surrounded 

 by it as by a sheath. When one of the cells in a hypha becomes 

 enlarged and surrounded with a heavy wall it is called a chlamydo- 

 spare. Some molds develop spores as a result of the union of 

 sex cells (sexual spores). These are called ascospores when pro- 

 duced in sacs (asci) and zygospores when formed by the union of 

 two like cells as in certain Phycomycetes. 



Spores of the molds are commonly born on hyphae that extend 



