BAD PRUNING. 175 



call crude sap, charged with material for the upbuilding of 

 the tree, is absorbed from the soil by the roots and is forced 

 upward, flowing through the trunk and branches to the 

 leaves, where it is elaborated by the evaporation of water 

 and the absorption of carbonic acid gas from the air. It 

 then finds its way throughout the whole tree, even to the 

 roots, passing through the soft bast cells of the inner bark 

 just outside the cambium layer, forming, as it goes, the new 

 wood and bark. 



It may be stated as a general rule that there can be no 

 perfect circulation of the sap and no long-continued growth 

 of new wood or bark on any branch or stump which supports 

 no leaves. It would appear, then, that roots, trunk and 

 branches have no inherent power of themselves to continue 

 growth and extension, but must depend upon the action 

 of the leaves to furnish that elaborated nutriment without 

 which their continued growth and development is impossible.* 

 If the new wood is formed by the sap in its descent from the 

 leaves, it evidently follows that if the projecting stump of 

 an amputated branch is left without leaves so 

 placed as to draw the sap to its farthest ex- 

 tremity, there to be elaborated and returned, 

 it must die.f 



Effect of Bad Pruning. The cut, Fig. 

 13, represents a stump left on a street tree 

 by the workmen employed in pruning trees 

 under the direction of the city forester of 

 one of our Massachusetts cities. Around 



. , ., , FIG. 13. Stump of a 



such an unprotected stump the rain and branch left by bad 

 other atmospheric influences soon begin the pruc 

 work of decay between the bark and the wood. The cam- 

 bium layer, lacking circulation, dries up ; insects enter ; 



* It is well known that the roots will for a time perform their functions without 

 the assistance of the leaves, and that growth of different parts of the tree occurs at a 

 time when there are no leaves upon it. But this growth is made by the absorption 

 of water by the roots and by the use of reserve material. If a tree is continually 

 deprived of its leaves until its reserve material is exhausted, it will die. 



t It is well known that there are some exceptions to this rule. Certain vigorous 

 trees will push out shoots from latent buds near the end of the amputated branch, 

 and leaves are formed, which by their functions enable the tree to cover the wound. 

 Willow trunks and branches deprived of their leaves and left upon the ground have 

 thrown out foliage and roots and grown into vigorous trees. 



