388 MICROORGANISMS 



uriant growth. When there is barely enough moisture pres- 

 ent in a given material to support a mold growth, the mycelium 

 development is very slight and there is little visible evidence 

 of the presence of the mold except the spores. The spores are 

 borne on very short sporophores and present a powdery 

 appearance over the surface of the substratum. It is common 

 to speak of mold when it presents this appearance as MILDEW. 

 Mildew is simply mold which has grown on a scant moisture 

 supply. During most of the year, the outdoor air and the air 

 in houses and, consequently, dry objects in this air are too dry 

 for the growth of molds. In the damp, sultry weather of the 

 summer time, however, the air sometimes becomes so damp 

 as to lend sufficient moisture to dry objects, such as clothing, 

 carpets, and the like, to permit a growth of mold on these 

 materials. Clothing hung in closed closets and the carpets of 

 unused rooms which are closed up, are more likely to suffer 

 from mold growth during damp, warm weather than if they 

 were well aired, for it has been found that air movement is 

 detrimental to the growth of mold. 



Molds will grow to some extent at comparatively low tem- 

 peratures, some even growing a little at only a few degrees 

 above freezing. For any rapid growth, however, a rather high 

 temperature is usually necessary. We take advantage of this 

 fact in keeping our food from molding between meals and over 

 night by putting it into a refrigerator. We should remember, 

 however, that the temperature of a refrigerator is sufficiently 

 high to permit of some mold growth, and for this reason we 

 should not attempt to keep food in a refrigerator very long. 



440. Effect of Mold Growth on Food. Food is not neces- 

 sarily ruined by the growth of mold in it. In fact, every time 

 we eat an apple that is partly decayed, we are likely to eat a 

 considerable quantity of mold which has already penetrated 

 the apparently sound parts of the apple. Similarly, when we 

 eat apple sauce or other similar food which has stood in a re- 

 frigerator for a day or more, we are likely to eat some mold 

 even though we are unable to detect it. An abundant growth 



