OF TRAINING. 25? 



the leaves and fruit to a hotter temperature than 

 would otherwise be gained, and in some measure to 

 ripen wood with more certainty. L 



That training a tree over the face of a wall will 

 protect the blossoms from cold must be apparent, 

 when we consider the severe effect of excessive eva- 

 poration upon the tender parts ; a merely low tempe- 

 rature will produce but little comparative injury in a 

 still air, because the more essential parts of the flower 

 are very much guarded by the bracts, calyx, and 

 petals, which overlie them, and, moreover, because 

 radiation (see page 136) will be intercepted by the 

 branches themselves placed one above the other, so 

 that none but the uppermost branches which radiate 

 into space will feel its full effects ; but, when a cold 

 wind is constantly passing through the branches' and 

 among the flowers, the perspiration, against which no 

 sufficient guard is provided by nature, becomes so 

 rapid (see page 129) as to increase the amount of cold 

 considerably, besides abstracting more aqueous mat- 

 ter than a, plant can safely part with. This being one 

 of the great objects of training trees, it is inconceiv- 

 able how any one should have recommended such 

 devices as those mentioned in the Horticultural Trans- 

 actions, ii. Appendix, p. 8, of training trees upon a 

 horizontal plane ; the only effect of which would be 

 to expose a tree as much as possible to the effect 

 of that radiation which it is the very purpose of train- 

 ing to guard against. 



The actual temperature to which a tree trained 

 upon a wall facing the sun is exposed is much higher 



