54 BACTERIA, YEASTS, AND MOLDS 



Water for their growth may be suppHed by the air in 

 which the food is kept, or by the food itself. 



1. The air is the source of the water when flour, which 

 naturally does not contain enough moisture to support 

 even molds, becomes covered with a growth of these organ- 

 isms. Flour is not the only material thus affected. A large 

 variety of materials in the household, ordinarily free from 

 molding, may show signs of mildew during a damp season. 

 The mustiness of a closed room is due to the presence of 

 molds, and is always an indication of dampness, for dry 

 rooms neither show signs of mold nor do they smell 

 musty. 



2. Some materials contain within themselves sufficient 

 water to produce a vigorous development of molds. Fruits, 

 for example, are so full of moisture that they are equally 

 good food for molds whether kept in a dry or a moist 

 place. // the mold once gets a start (which, by the way, is 

 very difficult in a dry atmosphere), the fruit itself furnishes 

 all necessary water. Jellies and other similar preserves also 

 contain sufficient moisture. 



From this it follows that food capable of being thoroughly 

 dried may be protected absolutely from molding if stored 

 in a dry place. It also follows that any condition which 

 favors moisture, such as darkness, stagnation of the air, 

 proximity to the soil (as in cellars), is likely to permit the 

 growth of molds. Under such conditions not only food, 

 but also leather-covered books, shoes, pocketbooks, and 

 even carpets or clothes may become covered with mildew. 

 In damp weather no animal or vegetable material is beyond 

 the possibility of molding ; but if it is placed in a dry atmos- 

 phere the growth of molds may be entirely prevented. 



