260 DISEASES OF TREES 



nourishment for the undiminished crown, which consequently 

 withers. The danger is avoided, and the plant gets over the 

 loss in a short time, if equilibrium between the roots and the 

 foliage is restored at the very first by shortening the longer 

 branches. 



A second reason for shortening the branches is the im- 

 provement of the shape of the plants, whether in the nursery or 

 in the wood. I do not intend in this place to enter upon the 

 technique of the subject, but will merely say that so far as the 

 growth of the plant is concerned the usual time namely, summer 

 is the least suitable. If we dress a plant in spring or autumn 

 we remove, in the main, only the branches, the reserve 

 materials being left in the storehouses of the stem. But if 

 summer be selected for the operation, the reserve materials of 

 the stem, being partially utilized in the production of shoots 

 and leaves, are lost. If one waits till autumn, the leaves of 

 the branches to be removed will have assimilated materials for 

 the following year, and these will have been partly deposited in 

 the main stem. It appears desirable to institute investigations 

 in this direction, and the question whether wounds are least 

 attacked by parasitic fungi, such as Nectria, during summer or, 

 during autumn and spring should also receive careful attention. 

 This question has special force with respect to Acer, Tilia, and 

 Aesculus, seeing that these genera suffer most from Nectria 

 cinnabarina, and in their case even small wounds should be 

 protected by grafting-wax. 



The practice of leaving snags destitute of buds on the main 

 stem is justly condemned, for the reason that if growth is rapid 

 they are partly embraced or completely enveloped when dead and 

 withered. On the other hand, it is a mistake to suppose that 

 decay spreads in the wood from such snags in after years, for I 

 have never been able to observe such a state of things even in 

 oaks that had been pollarded or coppiced in youth. 



As the wounds are small and are usually soon occluded by a 

 callus, the application of tar is scarcely necessary, except in the 

 case of the above-named trees, which are specially liable to suffer 

 from Nectria cinnabarina. The technical properties of timber 

 are not interfered with by the small brown wounds in the body 

 of the stem, for it must be borne in mind that numerous wounds 



