EVILS CAUSED BY TRAINING. 429 



of these can that motion be necessary to which some plants 

 are naturally exposed, and which, as has been already seen, 

 is of so much importance to the healthy maintenance of their 

 functions. Hence it is, that among fruit-trees the Vine never 

 suffers from being trained : indeed its anatomical structure is 

 specially suited to such a mode of existence ; while all erect 

 trees, of whatever kind, whose branches nature intended to be 

 rocked by the storm, and perpetually waved by the currents of 

 air to which they are exposed, in all cases suffer more 

 or less. 



One of the commonest and worst diseases induced by training 

 is a gradual impermeability of tissue to the free passage of sap, 

 which appears to stagnate, so that in time the branches become 

 debilitated and juiceless : the obstruction to the flow of the sap 

 tends to produce coarse shoots from various parts of the 

 branches, and especially from the roots. The cause of this 

 seems to be the too rapid deposit of the matter of lignification, 

 and to be induced by want of motion and excessive exposure of 

 the leaves and branches to the sun. The effect of the latter is 

 to inspissate all the juices, and to promote their formation; 

 while the former iacreases the evil by not keeping the fluids in 

 rapid circulation ; just as we know that a slow stream from a 

 muddy source deposits its impurities much more copiously 

 than a rapid stream. As this evil arises out of the operation of 

 training, and seems to be inseparable from it, there can be no 

 expectation of a remedy being discovered. 



The increase of the saccharine quality of fruit is by no 

 means an advantage in all cases ; it improves the Peach, the 

 Nectarine, the Pear, and the Plum, in which sweetness is the 

 great object : hut it deteriorates the Apple and the Apricot, 

 which are chiefly valued for their peculiar mixture of acidity 

 and sweetness. 



The protection received in the spring by trees trained upon 

 walls exposed to the sun, while it advances the period of 

 flowering, at the same time causes it to take place at a season 

 when they are not sufficiently secure from spring frosts ; and 

 hence the necessity of protecting such plants artificially by 

 coping, screens, bushes, curtains, and other contrivances. It 



