CHAPTER II. 



PHYSIOLOGY. 



Having described the different parts of the vine, let us see in what 

 manner and to what extent each of them contributes to the develop- 

 ment of the plant and production of fruit. 



The vine being a deciduous plant, the cycle of its yearly develop- 

 ment only extends from the time when the buds burst in the spring 

 till the leaves fall off in the autumn, which, in a temperate climate, 

 embraces a period of something under six -months; the other six 

 months of the year are passed in a dormant state. 



In this annual cycle of activity it seems to have for primary object 

 the production and proper maturation of its fruit; all the functions 

 of the different organs tending towards this end, as if they had been 

 brought into existence solely for this purpose. 



The activity culminates in the ripening of the fruit; after this 

 has taken place, the leaves turn red or yellow, fall off, and the plant 

 hastens to assume its wintry appearance. Not only is this the case 

 in the cultivated vine, where it might be expected since every device of 

 art and an artificial selection during many centuries have been at work 

 striving to increase the yield, but even in the wild state is this so, 

 although to a lesser degree. 



In the spring the activity of the vine begins to manifest itself by a 

 rise in the sap; this is followed by the emission of shoots bearing 

 leaves and flower buds, which grow with great rapidity for the first 

 few months. 



The rise of the sap is due to the increase in the surrounding tem- 

 perature; this acts by dilating the bubbles of air which exist in the 

 liquid column contained in the vessels of the stem; by stimulating the 

 leaf buds it causes the emission of organs which provide for a con- 

 tinuation of the rise. The vessels of the vine are large, and the sap 

 flows very freely through them. When a shoot is cut in the spring 

 it bleeds copiously. Hales measured this ascensional force of the 



