STATE OF THE SAP IN WINTER. 233 



II. 



Concerning the State in ivhich the true Sap of Trees is depofited 

 during Winter. By Thomas Andrew Knight, Efq*. 



IT is well known that the fluid, generally called the fap in The common 



trees, afcends in the fpring and fummer from their roots, fprinVandfum- 



and that in the autumn and winter it is not, in any confider- mer, but not in, 



able quantity, found in them ; and I have obferved in a former wincer ' 



paper, that this fluid rifes wholly through the alburnum, or 



fap-wood. But Du Hamel and fubfequent naturalifts have 



proved, that trees contain another kind of fap, which they 



have called the true, or peculiar juice, or fap of the plant. True or peculiar 



Whence this fluid originates does not appear to have been fa P 



agreed by naturalifts ; but I have offered fome facts to prove 



that it is generated by the leaf f ; and that it differs from the 



common aqueous fap owing to changes it has undergone in its 



circulation through that organ : and I have contended that from 



this fluid (which Du Hamel has called the Juc propre, and 



which I will call the true fap,) the whole fubftance, which is 



annually added to the tree, is derived. I fba!l endeavour in exifts in the 



the prefent paper to prove that this fluid, in an infpiffated j b " rnum ; 



* r r r " during winter: 



ftate, or fome concrete matter depofited by it, exifts during Its fubfequent 



the winter in the alburnum, and that from this fluid, or f u b_ de ^ inat,0ft 

 n t-rrii-i r l- r -i-i pointed out. 



itance, diflolved in the alcending aqueous lap, is derived the 



matter which enters into the compofition of the new leaves in 



the fpring, and thus furnifhes thofe organs, which were not 



wanted during the winter, but which are effential to the 



further progrefs of vegetation. 



Few perfons at all converfant with limber are ignorant, that That wJnter or 



the alburnum, or fap-wood of trees, which are felled in the autumn felled 



autumn or winter, is much fuperior in quality to that of other T° d haS ,ts 



. ' n J alburnum more 



trees of the fame fpecies, which are tuffered to fland till the firm, &c 



fpring, or fummer: it is at once more firm and tenacious in 



its texture, and more durable. This fuperiority in winter- commonly at- 



felled wood has been generally attributed to the abfence of the X*kmrt th* 



lap at that feafon ; but the appearance and qualities of the fap : 



* See Phil. Tranf. of 1S01, page 336. 

 | Philof. Tranf. 1805, p. 88. 



wood 



