1 8 Leading Principles of the Growth of Trees. 



be placed so accurately together that the sap may flow up 

 through the alburnum or sap-wood from the stock to the shoot, 

 and back again through the inner bark of the shoot to that 

 of the stock. When this union takes place, the rest of the cut 

 faces, even if some distance apart, are soon cemented by the 

 newly-forming wood, which fills all the vacant space. 



hi Budding, the newly-set bud is cemented to the wood of the 

 stock by the cambium, which hardens and fastens it. The next 

 spring the bud grows, forms a shoot, and the two portions become 

 securely united by the new wood. Unless there is enough of the 

 cambium to cement the wood to the stock, the operation cannot 

 succeed ; and this is the reason why, with vigorously growing 

 stocks, which are depositing much, budding succeeds better than 

 with feeble growers, where but little of this cement exists. 



The rapidity with which leaves exhale moisture, is shown by 

 severing them from the stem in dry weather. They soon wither 

 and become dry. Cut a shoot from a tree, and throw it down in 

 the sun's rays, and it will quickly shrivel, in consequence of the 

 rapid escape of its moisture through the leaves. But first cut off all 

 the leaves, and the shoot will remain plump a long time. This is 

 the reason that it becomes necessary to remove the leaves at once 

 from scions cut for budding. 



Hence also the reason that plants and trees are so liable to die if 

 transplanted with the leaves on, a disaster which may be partially 

 prevented in trees by removing the leaves ; and in plants or cuttings 

 with leaves on, by covering them immediately with a bell-glass, 

 which, by holding the watery vapor, keeps a humid atmosphere 

 about them. It is for this reason, also, that when young trees lose 

 a large portion of their roots, a part of the top must be cut off, to 

 prevent the heavy evaporation which all the leaves would occasion. 



A sunflower plant, about three feet high, was found to exhale 

 from its leaves in very dry weather between one and two pints of 

 water in a day. A bunch of growing grass placed beneath a cool 

 inverted glass, soon covered the sides of the glass with condensed 

 drops from the vapor, and in a few minutes the water ran down the 

 sides. These experiments show the great amount of water needed 

 by growing plants ; and also prove the mistake which some persons 

 commit, by leaving weeds to grow to shade the ground and keep it 

 moist, while these weeds are actually pumping the water rapidly 

 up from the soil, and dissipating it through their leaves. 



The absolute necessity of leaves to the growth of a tree is shown 

 by the fact that when they are stripped off by caterpillars, the tree 



