260 THE CULTURE OF FARM CROPS. 



seeds, and the stem is strengthened by the deposit of min- 

 eral matter in it, it follows that the woody fiber and the 

 ash of the stems ftre increased, not only directly, but rela- 

 tively by the decrease of starch sugar and albumen. 



The ripening of fruit which is a process closely related to- 

 the ripening of the seeds, is accompanied by an equally 

 considerable and interesting change. This change is more 

 intelligible than that which occurs in the ripening of seeds, 

 because it is one that can be produced by the chemist, and 

 its process and results represented by figures. 



The common fruits, the apple, pear, plum, grape, etc., in 

 their immature stage, are tasteless and consist almost wholly 

 of woody fiber, filled with flavorless sap and tinged with 

 the green coloring matter of the leaf chlorophyll. The 

 young fruit at this time performs some of the functions of 

 the leaf; absorbing carbonic acid and giving off oxygen; 

 and thus gathering carbon from the atmosphere and build- 

 ing up cellular tissue of this carbon and the water which it 

 receives from the roots. After a time the fruit becomes 

 sour by the formation of acid in it, and the acid gradually 

 increases. While this acid is increasing, less oxygen is giv- 

 en off than before. The process by which the fruit acids 

 and fruit sugar are produced may be explained as follows. 

 Tartaric acid (the acid of grapes) is represented by the for- 

 mula 4 H4 65; or 4 equivalents of carbon; 4 of hydrogen 

 and 5 of oxygen. This acid may be formed in the fruit in 

 two ways : either from the carbonic acid absorbed by the - 

 grape, and water, with the exhalation of oxygen; or from 

 the gum and sugar always in the sap by the absorption of 

 oxygen from the atmosphere. Thus 



4 parts of Carbonic acid = 4 Os 

 2 parts of Water = H 4 O 2 



The sum is = 4 H4 Oio 

 Tartaric acid = C 4 H 4 O 5 



leaving O 



