102 Mr. Knight concerning the State in which 
sweetness in decoctions of the sycamore wood in winter. I am 
therefore inclined to believe that the saccharine matter existing 
in the ascending sap is not immediately, or wholly, derived 
from the fluid which had circulated through the leaf in the 
preceding year ; but that it is generated by a process similar to 
that of the germination of seeds, and that the same process is 
always going forward during the spring and summer, as long 
as the tree continues to generate new organs. But towards the 
conclusion of the summer I conceive that the true sap simply 
accumulates in the alburnum, and thus adds to the specific 
gravity of winter-felled wood, and increases the quantity of its 
extractive matter. 
I have some reasons to believe that the true sap descends 
through the alburnum as well as through the bark, and I have 
been informed that if the bark be taken from the trunks of trees 
in the spring, and such trees be suffered to grow till the fol- 
lowing winter, the alburnum acquires a great degree of 
hardness and durability. If subsequent experiments prove that 
the true sap descends through the alburnum, it will be easy to 
point out the cause why trees continue to vegetate after all 
communication between the leaves and roots, through the bark, 
has been intercepted : and why some portion of alburnous 
matter is in all trees * generated below incisions through the 
bark. 
It was my intention this year to have troubled you with some 
observations on the reproduction of the buds and roots of trees ; 
• I have in a former paper stated that the perpendicular shoots of the vine form an 
exception. I spoke on the authority of numerous experiments ; but they had been 
made late in the summer ; and on repeating the same experiments at an earlier period, 
I found the result in conformity with my experiments on other trees. 
