64 PLANTING. 



sponding series of vessels formed in the stem from its point of emitting 

 the branch to the root, it is clear that a branch not only increases in sub- 

 stance by the functions of its own organization, but must, of a necessity, 

 periodically increase the substance or diameter of the trunk. 



The results of practice agree with this ; for if an overgrown limb or 

 branch of a free-growing tree be pruned off, the annual increase of the 

 diameter of the stem is not found to exceed its previous rate of increase; 

 or the excess, if any, is not equal to the contents of wood which had 

 been periodically formed by the branch or branches thus separated from 

 the stem*. 



It is reasonable to inquire, if the sap or nutritive fluid, periodically sup- 

 plied by the roots immediately connected with the large branch taken off 

 goes not to a proportionate increase of the stem, to what channel is it 

 directed? It has already been mentioned (in Chapter III.) that the 

 vessels which convey the periodical supply, and the roots which collect it, 

 are annually produced ; and the fact is, that when the primary organs and 

 stimulus of production, (i. e. the leaves and green system of the plant,) 

 are taken away, the annual rootlets and spongeols connected with these 

 vessels cease to be renewed, until another branch, or series of branches, 

 are reproduced by the vital power acting on the sap in the vessels of the 

 stem connected with the numerous latent germs of buds in the bark near 

 to the wound, or those dispersed in its neighbourhood. Hence it is, also, 

 that should the season of the year of pruning the branch be that in which 

 the sap is accumulated in the largest quantity in the leaves, and in the 

 smallest proportion in the vessels, scarcely any reproduction of branches 

 follows the operation of pruning ; and hence, also, the different effects of 

 summer and of winter pruning as regards this point. 



When branches are not allowed to perfect one year's growth, but are 

 pruned off annually within a bud or two of their origin with the stem, they 

 act rather as organs of waste than those of increase of wood to the stem. 

 But although the rate of periodical increase of the diameter of a tree 

 be thus lessened, in a certain extent, by the loss of a full grown lateral 

 branch, yet the. increase of the stem in height or length is not thereby 

 retarded, the ligneous vessels of the root corresponding with those of the 

 stem or wood, probably act with but little diminished force in sending up 

 sap to the higher extremities of the treef. 



It is of great importance that branches which indicate an over-luxuriant 

 growth should never be suffered to become large, or to exceed the 

 medium si/e of the majority of the boughs of the tree, but should be 

 pruned off close to the stem when the general interests of the plant will 

 admit of it. These over-luxuriant branches, which, when suffered to take 

 the lead in growth of the general boughs, become so hurtful to the per- 

 fection dl 'growth of the stem, are evidently produced and supported by the 

 accidental circumstance of a superior portion of soil being in the way of, 



* In numerous and varied trials made by the writer to ascertain this point, the results 

 have always ^one to prove tl e above facts. 



f In a few instances, for the sake of particular effect, and to enable carriages to pass, 

 then- have bn-n, at Ulair Adam, limbs of considerable si/.e cut from oaks of tifty years 

 old and upwards. The cut would have been horizontal ; but by making the surface of 

 much greater si/e, they were made j erpendicular. Uy ^reat attention, all injury was 

 prevented to the trunk, and the wounds arc now healed over (at the distance, of twelve 

 or fifteen years from the date of the operation). Whether it has accelerated or retarded 

 the diameter-growth <,r thickness of the trees cannot be stated, as observation was not 

 called to it, but they have certainly increased as much in that respect as the trees around 

 them of the same sort and a^e. In one instance, the cutting of a limb, where the tree 

 cleft, has bad the effect of setting the other stem upright, so that it appears now exactly 

 in the perpendicular line, and like the original stem of the tree. 



