DESCENT OF THE SAP IN TREES. 99 



no doubt, but that the new matter thus deposited owed its formation 

 to a portion of sap which descended by gravitation from the leaves 

 growing between the wounded parts and the principal stems. 



The result of this experiment appears to point out one of the causes 

 why perpendicular shoots grow with much greater vigour than others ; 

 they have probably a more perfect and more rapid circulation. 



The effects of motion on the circulation of the sap, and the consequent 

 formation of wood, I was able to ascertain by the following expedient. 

 Early in the spring of 1801 I selected a number of young seedling 

 apple-trees, whose stems were about an inch in diameter, and whose 

 height, between the roots and first branches, was between six and seven 

 feet. These trees stood about eight feet from each other ; and. of 

 course, a free passage for the wind to act on each tree was afforded. By 

 means of stakes and bandages of hay, not so tightly bound as to impede 

 the progress of any fluid within the trees, I nearly deprived the roots 

 and lower parts of the stems of several trees of all motion, to the height 

 of three feet from the ground, leaving the upper parts of the stems and 

 branches in their natural state. In the succeeding summer, much new 

 wood accumulated in the parts which were kept in motion by the wind ; 

 but the lower parts of the stems and roots increased very little in size. 

 Removing the bandages from one of these trees in the following winter, 

 I fixed a stake in the ground, about ten feet distant from the tree, on 

 the east side of it ; and I attached the tree to the stake, at the height 

 of six feet, by means of a slender pole about twelve feet long ; thus 

 leaving the tree at liberty to move towards the north and south, or more 

 properly, in the segment of a circle of which the pole formed a radius ; 

 but in no other direction. Thus circumstanced, the diameter of the 

 tree from north to south, in that part of its stem which was most 

 exercised by the wind, exceeded that in the opposite direction in the 

 following autumn, in the proportion of thirteen to e even. 



These results appear to open an extensive and interesting field to our 

 observation, where we shall find much to admire, in the means which 

 nature employs to adapt the forms of its vegetable productions to every 

 situation in which art or accident may deposit them. If a tree be placed 

 in a high and exposed situation, where it is much kept in motion by 

 winds, the new matter which it generates will be deposited chiefly in the 

 roots and lower parts of the trunk ; and the diameter of the latter will 

 diminish rapidly in its ascent. The progress of the ascending sap will 

 of course be impeded ; and it will thence cause lateral branches to 

 be produced, or will pass into those already existing. The forms of 



