Microorganisms in Relation to Man 



551 



cloud-like dust when disturbed. Disturb the mold in one of 

 your cultures in a single ray of sunlight admitted into a darkened 

 room. The number of spores thus 

 scattered is practically countless. The 

 spores float easily in gently moving air 

 and are widely distributed. As seeds 

 they grow wherever they find suitable 

 conditions, and produce more spores. 



In specimen No. 1, you will probably 

 find no sign of growing life or mold. This 

 may lead to the conclusion that where 

 spores have not been planted, mold will 

 not appear. If your control is in good 

 condition, expose it to the air near the 



floor of a room when people are moving 



, . , . . . r, ,, FIG. 165. Development 



about, or inoculate it with the spores from of gpores in brown and gray . 



another culture. If the latter, note the green molds ; o, ripe branch 

 color of the spores. Observe as directed ready to scatter spores ; b, a 

 for the others. y un % branch. 



Molds are small thread-like plants easily visible to the unaided 

 eye. They are included in a larger group of plants, called 

 fungi. The fungi include several other groups of plants, such 

 as mushrooms, toadstools, the various smuts and rusts, and 

 the groups of much smaller plants called yeasts. The fungi 

 as a class or group are included in the large general group 

 Plants. Closely related to the fungi or spore-producing plants 

 is a group of plants called bacteria. Bacteria are microscopic 

 in size, reproducing generally by simple division or fission. 

 The two groups, fungi and bacteria, are not, however, sharply 

 distinguished, and the terms are often used interchangeably 

 in discussion. The border species between the two groups are 

 not clearly differentiated and may easily be assigned to one 

 class or the other. 



275. Varieties of fungi. There are many varieties of fungi, 

 which are generally distinguished by differences in size and 

 color. Some may be as large as the puffball or giant toadstool, 



