u 



We, therefore, see that the leaves do not simply act beneficially by 

 sheltering the grapes from the direct rays of the sun, but are indis- 

 pensable for the elaboration of the necessary constituents of the mature 

 fruit. The unripe berries contain several free acids, amongst the 

 number tartaric, citric, and malic are the most important. By the 

 action of these acids on such substances as starch, gum, dextrine, 

 lignine, cellulose, &c., grape-sugar or glucose is formed. The fruit 

 during this time becomes richer in sugar and poorer in acid ; part of 

 the acid is also neutralized by mineral salts absorbed by the roots, 

 and at the same time the juice becomes denser through loss of water 

 by evaporation. The different processes which take place in the 

 plant, of which the ultimate result is the production of glucose, are 

 exceedingly complex and cannot be gone into here ; the above out- 

 line sketch will suffice to give an idea of the character of the 

 transformations. 



A short time before the maturation takes place -the time being 

 marked for red grapes by their commencing to change colour a 

 characteristic change seems to come over the vine; it looks sick. 

 This is caused by the sap partly leaving the leaves and transporting 

 itself to the berries. During this time the plant looks more unhealthy 

 than at any other period of its yearly development. This is termed in 

 French the " veraison" and continues, although in a less marked 

 manner, until the time when the fruit is ready to be picked. 



Once the maturity is complete, whether the grapes be picked or not, 

 the duty of the year being accomplished, the vine hastens to assume 

 its winter appearance. The nutritive materials which have not been 

 required for the fruit are concentrated in or about the buds as a store 

 for next year, to enable the plant to start its growth again. 



The leaves turn red or yellow and fall off ; the ascensional power 

 of the sap becomes less and less and finally ceases, and the vine 

 assumes its winter or dormant state and is to all intents and purposes 

 dead. It continues in this state until the rise of temperature in the 

 spring determines a rise of sap and commencement of vegetation, when 

 the same cycle is gone through once more. 



