COMMON BLACK MOLD. 



Mucor stolonijer (Rhizopus nigricans}. 



THALLOPHYTES J FUNGI) PHYCOMYCETES. 



PRELIMINARY. 



THE molds are quite common, appearing on stale 

 bread, damp leather, and decaying fruits, sometimes 

 as grayish fluffy masses and sometimes as blue or yellow 

 coatings to their substrata. Mucor may usually be 

 grown quite readily upon a sweet potato or a piece of 

 moist bread kept at favorable temperature in a closed 

 glass dish or under a glass bell. 



Although it is an easy matter to obtain molds which 

 reproduce themselves by asexual spores, it is usually 

 quite difficult to induce them to undertake sexual pro- 

 cesses. It is supposed that Mucor plants have almost 

 discontinued reproduction by means of sexual spores. 

 However, zygospores may sometimes be obtained by 

 growing the material under a glass cover, keeping it 

 moist, and not in direct sunlight, and maintaining a 

 constantly favorable temperature of 22 to 25 C. 1 



1 In a brief article on " Sexual Reproduction in the Mucorinese " by 

 A. F. Blakeslee in Science, 19: 864, 1904, and an extended discussion 



55 



