24 THE FRUIT GROWER'S GUIDE. 



supported by the same roots, each variety retains its own peculiar flavour and time of 

 ripening. The change is effected by the absorption of gases, oxygen being the most 

 active agent in the ripening. " Six equivalents of tartaric acid," according to Liebig, 

 by absorbing " six equivalents of oxygen from the air, form grape sugar, separating 

 at the same time twelve equivalents of carbonic acid." That being so the supreme 

 importance of a free circulation of air when fruits are ripening in glass structures 

 becomes apparent. But other chemical changes occur in ripening fruit, such as the 

 conversion of mucilage and starch into saccharine matter by the action of warmth and 

 acids. Thus many, or most, fruits ripen after being gathered when the heat is sufficient 

 to incite fermentation; therefore their ripening may be facilitated or retarded by a 

 regulation of the temperature. Woody fibre and cellular tissue are also converted into 

 sugar when fruits are ripening, hence hard and tasteless pears become soft and sweet. 

 The relative changes that occur in the constituents of fruit from youth to maturity 

 are represented by the following figures, from Johnston's Agricultural Chemistry, which 

 apply to three stages of growth of the peach. 



Unripe. Riper. Fully ripe. 



Sugar 



Gum 



Cellulose 



Malic acid 



Vegeta 



Water 



The increase of sugar during the ripening period, and the corresponding 

 decrease of acid and vegetable matter, and also of water, is clearly shown, and such 

 facts are as beacon lights for the cultivator to guide him on the path that leads 

 to success. 



They demonstrate that more water, both at the roots and in the atmosphere, is needed 

 during the swelling period than subsequently when ripening commences; the chief essen- 

 tials at this later stage being adequate moisture and a free circulation of pure fresh air, 

 for if the air is impure or unpleasant from any cause, its impurities will be absorbed by the 

 fruit, and, instead of its being delicious to the palate, it may be repulsive. It is impos- 

 sible that the surroundings of ripening fruit can be too sweet and clean, and in conse- 

 quence of inattention to this simple but highly important matter much fruit is impaired 

 in quality yearly if not spoiled. 



