216 PRINCIPLES OF GARDENING. [CH. VII. 



lents of oxygen from the air, form grape sugar, 

 separating at the time twelve equivalents of carbonic 

 acid." 



This, however, is not the only decomposition taking 

 place whereby sugar is formed in ripe fruit, but there 

 is sufficient reason to believe that its mucilage and 

 starchy constituents are converted into saccharine 

 matter by the combined agency of warmth and the 

 acids. It is thus that apples are rendered so much 

 sweeter by baldng, and M. De Candolle states that 

 the pulp of apple dissolved in water with a vegetable 

 acid is converted into sugar ; that gummy matter 

 obtained from starch and mixed with tartaric acid 

 aided by warmth effects a similar transmutation ; 

 and M. Kirchoff proved long since that starch, 

 digested at a gentle heat ^\ith diluted sulphuric acid, 

 became sweet. 



During the ripening process, both of fruit and seed, 

 all plants give out more carbonic acid and less oxygen 

 than during the earlier stages of their growth, and 

 thus is given a reason why room plants should be 

 removed when once past their meridian vigour. 



Now to effect these changes, to ripen perfectly, 

 that is to generate its best proportions of sugar and 

 aroma, every plant requires a certain amount of sap, 

 light, heat, air, and moistui'e ; and how these are best 

 secured to them, so far as training and the atmosphere 

 around them is concerned, may be here appropriately 



