48 THE FRUIT-TREE AND SHRUB PRUNER. 



required for colouring Grapes, and not light or high 

 cultivation. Here we solve the difficulty, and ascer- 

 tain the cause why early house Grapes will not colour, 

 viz. a high temperature and want of sufficient air. 



It is not the high temperature that will do it without 

 the same proportion of air. The oxygen acts upon the 

 juices of the fruit, and changes the colour in proportion 

 to the extent in which that gas is present. This is the 

 whole theory of the subject. 



There are features relating to the cultivation of the 

 Grape which do not actually come under my present 

 notice in a work on pruning only ; but I may men- 

 tion a plan I used to adopt for the admission of air 

 into a house I had for Grapes. As the sashes of early 

 graperies can seldom be opened, some means for the 

 admission of air should be resorted to, and I have found 

 that openings made in the front wall of the house close 

 to the ground, about nine inches square, fitted with 

 sliding shutters, are a most excellent method, supposing 

 the house to be a lean-to, and the pipes close to the 

 floor along the front. There can be no doubt but that 

 is the proper place for them. Then these shutters may 

 be opened every morning at nine o'clock, let the weather 

 be what it may, except during a sharp cutting wind or 

 frost. In fact they may be left open night and day 

 from the beginning of May until the end of the summer, 

 without any danger whatever ; for if a good brisk heat 

 is kept up in the pipes, the air coming in contact 

 immediately with the hot pipes gets sufficiently heated 

 to prevent any chill to the air of the house. _ Moreover, 

 the heat gives vitality and speed to the air admitted, 

 which is immediately distributed among the leaves and 

 fruit, even causing a slightly visible motion to the 

 leaves of the Vines, which is an evident token of its 

 circulation. The openings may be three feet, a few 

 inches more or less, apart. 



