THE EFFECTS OF STORAGE OX FRUITS 131 



storage house, there is much less damage resulting from 

 the effects of these decay organisms. 



Paper wrappers are of especial importance because of 

 their insulating value against the spread of the fungus 

 growth. It takes from two to six weeks for the fungus 

 to go through its complete life cycle. Then as the spores 

 are given out they float through the air and finally 

 lodge upon new or uninfected places. Where the wraps 

 are put on in good shape it tends to keep the infected 

 fruit separated from the others and prevent the spread 

 of the decay organisms. 



Physiology of Fruit. While there is still a great op- 

 portunity for the study of the physiology of fruits, a 

 few things that are now known may be noted in connec- 

 tion with the keeping of fruit in storage. Certain sub- 

 stances are always present in the chemical make-up of 

 fruits and more or less definite changes are known to 

 take place. By far the greatest percentage of all fruit 

 is water, running as high as 90% in fruit like straw- 

 berries and from 75 to 85% in apples, pears, etc., and 

 down as low as 60 or 65% in some of the stone fruit 

 which have a large seed or pit. Most fruits contain 

 various carbohydrates such as the fruit sugars, cellulose 

 and pectin bodies, and there are also certain acids or 

 alkaloids present in almost every kind. 



The apple contains malic acid which gives it its char- 

 acteristic flavor and aroma, while the citrus fruits have 

 the citric acid, etc. These are purely vegetable acids 

 and are difficult to classify from the chemical stand- 

 point. Most fruits contain a certain amount of tannin, 

 especially pome fruits. This, when exposed to the air, 

 is changed into tannic acid by oxidization and is re- 



