MOTION OF THE SAP IN T^IEES. 



109 



tendril, of the vine, had been successfully substituted, in many instances, 

 for each other ; but that I had failed in my efforts to engraft a bunch of 

 grapes, by approach, on the leaf-stalk ; owing, I conceived, to the 

 operation having been improperly performed. In those experiments, I 

 cut the leaf-stalk into the form of a wedge, and made an incision in the 

 fruit-stalk adapted to receive it ; but, under such circumstances, the leaf- 

 stalk (as I had proved by many experiments) has no power to generate 

 new matter ; and the wounds of the fruit-stalk heal so slowly that I 

 readily anticipated the ill success of the operation. In the last spring, I 

 pared off similar portions of the leaf-stalk and fruit-stalk ; and, bringing 

 the wounded parts into contact, I secured them closely together, by 

 means of a bandage, letting the leaf remain. Under these circumstances 

 a union took place ; and the fruit-stalk being then taken off below the 

 point of junction and the leaf-stalk above it, the grapes drew their whole 

 nutriment through the remaining part of the leaf-stalk. They did not, 

 however, acquire their full size ; and the seeds were small, and, I think, 

 incapable of vegetating ; but this I attribute to the want of nutriment in 

 quantity rather than in quality ; for the union of the vessels of the leaf- 

 stalk with those of the fruit-stalk was very imperfect. The grapes, 

 which were the purple Frontignac, possessed their musky flavour in the 

 same degree with others growing on the same plant. 



There is another experiment in my last paper, which I will also notice 

 here ; because it appears to lead to some important conclusions, and had 

 been tried only in a single instance. I have there stated, that the stem 

 of a young tree became elliptical, by being confined to move only in the 

 segment of a large circle. This experiment was successfully repeated, 

 during the last year, on other trees ; but I have nothing to add to the 

 description which I have already given. 



V. OBSERVATIONS ON THE STATE IN WHICH THE TRUE SAP OF TREES 

 IS DEPOSITED DURING WINTER. 



[Read before the ROYAL SOCIETY, January 24, 1805.] 



IT is well known that the fluid, generally called the sap in trees, ascends 

 in the spring and summer from their roots, and that in the autumn and 

 winter it is not, in any considerable quantity, found in them ; and I have 

 observed in a former paper, that this fluid rises wholly through the 

 alburnum, or sap-wood. But Duhamel and subsequent naturalists have 

 proved, that trees contain another kind of sap, which they have called 



