THE PREMATURE DEATH OF THE BRANCHES OF WALL FRUIT-TREES. 337 



Philosophical Transactions, that the forms of all large and old trees 

 must have been much modified by this agent. The motions of the 

 circulating fluids, and sap of the tree, are also greatly influenced and 

 governed by it ; and whenever any part of the root, the stem, or the 

 branches of a tree are bent by winds or other agents, an additional 

 quantity of alburnum is there deposited ; and the form of the tree 

 becomes necessarily well adapted to its situation, whether that be 

 exposed or sheltered. If exposed to frequent and strong agitation, 

 its stem and branches will be short and rigid, and its superficial roots 

 will be large and strong ; and if sheltered, its growth will be in every 

 part more feeble and slender. I have much reason to believe, upon 

 the evidence of subsequent experiments, that the widely-extended 

 branches of large timber- trees would be wholly incapable of supporting 

 their foliage when wetted with rain, if the proportions of their parts 

 were not to be extensively changed and their strength greatly aug- 

 mented by the operation of winds upon them during their previous 

 growth. Exercise, therefore, appears to be productive of somewhat 

 analogous effects upon vegetable and upon animal life, and to be nearly 

 as essential to the growth of large trees as to that of animals. 



Whenever the branches of a tree are bound to a wall, they wholly lose 

 the kind of exercise above described, which nature obviously intended 

 them to receive ; and many ill consequences generally follow not, how- 

 ever, to the same extent, nor precisely of the same kind, to trees of 

 different species and habits. When a standard plum or peach tree is 

 permitted to take its natural form of growth, its sap flows freely 

 and most abundantly to the extremities of its branches, and it con- 

 tinues to flow freely through the same branches during the whole life 

 of the tree : but when the branches are bound to a wall, and are no 

 longer agitated by winds, each branch becomes in a few years what 

 Duhamel calls ; " usee," that is, debilitated and sapless, owing apparently 

 to its being no longer properly pervious to the ascending sap, This 

 obstruction to its ascent causes luxuriant shoots to spring from the lower 

 parts of the tree ; and these are in succession made to occupy the places 

 of the debilitated older branches by the process which the gardener 

 calls "cutting in." 



The branches of the apricot, and particularly of the Moor-park 

 varieties, often die suddenly, owing to the same cause, with much more 

 inconvenience and loss very frequently to the gardener ; for trees of this 

 species do not usually afford him the means of filling up vacancies upon 

 his wall, as those of the peach and plum do. 



