54 AGRICULTURAL AND INDUSTRIAL BACTERIOLOGY 



cell develop into sacs. In each one of these sacs, or asci, 

 two or more spores, usually eight, form. The structure 

 developed surrounding the spore sacs is termed a pertihe- 

 cium. This is usually globular in shape and frequently 

 brightly colored. Comparatively few of the molds usually 

 encountered in the laboratory produce these perithecia. 

 An exception is to be found in certain common species of 

 Aspergillus, which readily develop orange or bright yellow 

 perithecia under suitable conditions. 



Asexual Reproduction in Molds. — The asexual spores of 

 molds may be developed free or they may be enclosed in 

 special spore cases termed sporangia. Many of the molds 



Fig. 35. — Formation of asoospores and asci in Asperillus. 1, 2, 

 3. Stages in the development of a perithecium. 4. A single ascus 

 from interior of the perithecium. (Adapted from De Bary. ) 



with nonseptate hyphae produce these sporangia, but they 

 are never developed by the molds with septate hyphae. 



Sporangium Formation. — The development of the spo- 

 rangium may be illustrated by the genus Mucor. The first 

 evidence of spore formation is the appearance of a fertile 

 hypha produced at right angles to the surface on which the 

 mold is growing. This becomes enlarged at the end, in- 

 creases in length, and finally consists of a relatively long 

 thread with a much swollen tip. The interior of the latter 

 is filled with protoplasm containing numerous nuclei. A 

 special wall then forms extending from the tip of the thread 

 up into the swollen apex. The nuclei surround themselves 

 by bits of protoplasm and develop around these, in turn. 



