46 BACTERIA, YEASTS, AND MOLDS 



This is no easy matter, for there are almost sure to be 

 some depressions in the skin, such as cracks or dents, and 

 in these moisture is sure to accumulate. The depressions 

 around the stem or the eye of an apple serve the same 

 end, and, in damp air, water is so likely to accumulate 

 here that molding starts readily. Once germinated the 

 threads quickly force their way into the apple around the 

 stem and find plenty of moisture in the flesh of the fruit. 

 Hence any devices which tend to keep the skin of the 

 fruit dry are at the same time devices for checking the 

 first steps of decay. Fruit whose skin is wiped frequently 

 with a dry cloth will keep better than fruit that is not 

 thus wiped. This question of moisture explains also 

 why it is that fruits begin to decay first at points where 

 two pieces come in contact with each other, since here 

 there is a much better opportunity for moisture to con- 

 dense. We also learn why fruit which has been cooled 

 to a very low temperature — as in cold storage — and 

 subsequently warmed, may decay more quickly than fruit 

 which has not been cooled. The cold skin of the fruit 

 taken from cold storage causes a slight condensation of 

 water, and then when subsequently warmed this water 

 furnishes a favorable starting point for the germination 

 of mold spores. This explains also why covering with 

 sawdust or charcoal is of great value in checking the 

 decay of fruit. If packed in sawdust, fruit may be pre- 

 served a long time, because the sawdust absorbs moisture 

 and prevents the accumulation of water upon the fruit 

 skin. Charcoal serves the same purpose. For some 

 fruits, like pears, oat chaflf or rye chaff serves better 

 than sawdust. 



