of THE WOOiy. 



Malpighi and Grew thought it was fonned 

 bj the bark, and the best observations have 

 confirmed their opinion. Hales supposed the 

 wood added a new layer to itself externally 

 every year. Linneeus had a peculiar notion, 

 that a new layer of wood was secreted annu- 

 ally from the pith, and added internally to 

 tlie former ones. Truth obliges us to confess 

 that the latter theory is most devoid of any 

 kind of proof or probability. 



Du Hamel, by many experiments, proved 

 the V. ood to be secreted or deposited from 

 the innermost part of the bark or liber. He 

 introduced plates of tinfoil under the barks 

 of growing trees, carefull}^ binding up their 

 wounds, and, after some years, on cutting 

 them across, he found the layers of new wood 

 oil the outside of the tm. His original spe- 

 cimeric \ h;rve examined in the public mu- 

 seum at Pans. 



Dr. Hope, the latn worthy Professor of 

 Botany at Edinburgh, instituted an experi- 

 ment, if possible mare decisive, upon a branch 

 of Willow three or four j-ears old. The bark 

 was care I ally cut throucrh lonoitudinaliy on 

 one side for the leno'th of several inches, so 



