Mr. Knight concerning the State , &c. Sg 
the winter in the alburnum, and that from this fluid, or sub- 
stance, dissolved in the ascending aqueous sap, is derived the 
matter which enters into the composition of the new leaves in 
the spring, and thus furnishes those organs, which were not 
wanted during the winter, but which are essential to the 
further progress of vegetation. 
Few persons at all conversant with timber are ignorant, that 
the alburnum, or sap-wood of trees, which are felled in the 
autumn or winter, is much superior in quality to that of other 
trees of the same species, which are suffered to stand till the 
spring, or summer : it is at once more firm and tenacious in 
its texture, and more durable. This superiority in winter- 
felled wood has been generally attributed to the absence of the 
sap at that season ; but the appearance and qualities of the 
wood seem more justly to warrant the conclusion, that some 
substance has been added to, instead of taken from it, and 
many circumstances induced me to suspect that this substance 
is generated, and deposited within it, in the preceding summer 
and autumn. 
Du Hamel has remarked, and is evidently puzzled with the 
circumstance, that trees perspire more in the month of August, 
when the leaves are full grown, and when the annual shoots 
have ceased to elongate, than at any earlier period ; and we 
cannot suppose the powers of vegetation to be thus actively 
employed, but in the execution of some very important opera- 
ration. Bulbous and tuberous roots are almost wholly generated 
after the leaves and stems of the plants, to which they belong, 
have attained their full growth ; and I have constantly found, 
in my practice as a farmer, that the produce of my meadows has 
been immensely increased when the herbage of the preceding 
MDCCCV. N 
