PREFACE. 



XI 



the buds with nearly as much rapidity as ever, so that the accumulation is but 

 imperfectly produced. On this account the second practice, of bending branches 

 downwards is found to be attended with more certain consequences. The effect 

 of turning the branches of a tree from thair natural position to a pendulous or a 

 horizontal one is, to impede both the ascent and the descent of the fluids in a gra- 

 dual but certain manner. The tissue of which branches are composed is certain- 

 ly permeable to fluids in every direction; and there can be no doubt that the vital 

 action of the vessels of a plant is performed both in the natural and in an invert- 

 ed position. So long as that erect direction of the branches which is natural to 

 them is exactly maintained, the flow of their fluids, being subject to no interrup- 

 tions, will take place in the freest possible manner; but the moment this natural 

 direction is deviated from, the vessels become more or less compressed, their action 

 is impeded, and finally, if the inversion is perfect, it becomes so slow that an 

 accumulation of the proper juices necessarily takes place through every part of 

 the system. 



" One of the objects of training is to produce the same effect. Branches are 

 bent more or less from their naturally erect position ; their motion, in consequence 

 of the action of winds upon them, which is known to facilitate the movement of 

 the fluids, is totally destroyed ; and hence arises the accumulation of proper juice 

 which is necessary to their fertility. Nor is the injiuence of the stock of an es- 

 sentially different nature. In proportion as the scion and the stock approach 

 each other closely in constitution, the less effect is produced by the latter ; and, 

 on the contrary,, in proportion to the constitutional difference between the stock 

 and the scion, is the efl^ect of the former important. Thus, when Pears are 

 grafted or budded on the wild species. Apples upon Crabs, Plums upon Plums, 

 and Peaches upon Peaches or Almonds, the scion is, in regard to fertility, exactly 

 in the same state as if it had not been grafted at all. While, on the other hand, 

 'a great increase of fertilhy is the result of grafting Pears upon Quinces, Peaches 

 upon Plums, Apples upon Whitethorn, and the like. In these latter cases, the 

 food absorbed from the earth by the root of the stock, is communicated slowly 

 and unwillingly to the scion; under no circumstances is the communication 

 between the one and the other as free and perfect as if their natures had been 

 more nearly the same ; the sap is impeded in its ascent, and the proper juices 

 are impeded in their descent, whence arises that accumulation of secretion which 

 is sure to be attended by increased fertility. No other influence than this can be 

 exercised by the scion upon the stock. Those who fancy that the contrary takes 

 place ; that the Gluince, for instance, communicates some portion of its austerity 

 to the Pear, can scarcely have considered the question physiologically, or they 

 would have seen that the whole of the food communicated from the alburnum of 

 the Q.uince to that of the Pear, is in nearly the same state as when it entered the 

 roots of the former. Whatever elaboration it undergoes must necessarilv take 

 place in the foliage of the Pear ; where, far from the influence of the Quince, 

 secretions natural to the variety go on with no more interruption than if the 

 Quince formed no part of the system of the individual. 



" If we consider upon what principle the fiaxour of particular fruits may he 

 improved, we shall find that it is entirely due to the increased action of the vital 

 functions of leaves. When the sap is first communicated by the stem to the 

 leaves, it has experienced but few chemical changes since it first entered the 

 roots. Such changes as it has undergone have been due rather to the solution 

 of some of the pre-existing pecuhar secretions of the individual by the sap in 

 its way upwards through the alburnum, than to any other cause. As soon, how- 

 ever, as it enters the leaves, it becomes altered in a variety of ways, by the com- 

 bined action of air, and light, and evaporation ; for which purposes the leaf is 

 admirably adapted by its anatomical structure. Thus altered in the leaves, it 

 ceases to be what we call sap, but becomes the proper juice ; or, in other words 

 acquires the peculiar character of the final secretions of the individual from 

 which it IS formed. Discharged by the leaves into the bark, it is then conveyed 

 by myriads of channels of cellular substance throughout the whole system. 

 From these secretions, of whatever nature they may be, the fruit has the power 

 of attracting such portions as are necessary for its maturation. Hence it follows, 

 that the more we can increase the pecuHar secretions of a plant, the higher will 

 become the quaUty of its fruit ; and that, on the other hand, the less the plant is 

 m condition to form those secretions, the less will be the quality of the fruit It 



