OF THE WOOD. 27 



every year. Linnasus had a peculiar notion, that a 

 new layer of wood was secreted annually from the pith, 

 and added internally to the former ones. Truth obliges 

 us to confess that the latter theory is most devoid of 

 any kind of [n'oof or probability. 



Du Ilamel, by many experiments, proved the wood 

 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, carefully binding up their 

 ■wounds, and, after some years, on cutting them across, 

 he found the layers of hew wood on the outside of the 

 tin. His original specimens 1 have examined in the 

 public museum at Paris. 



Dr. Hope, the late worthy Professor of Botany at 

 Edinburgh, instituted an experiment, if possible more 

 decisive, upon a branch of Willow three or four years 

 old. The bark was carefully cut through longitudinally 

 on one side for the lencrth of several inches, so that it 

 might be slipped aside from the wood in the form of 

 a hollow cylinder, the two ends being undisturbed. 

 Tlie edges of the bark were then united as carefully as 

 possible, the wood covered from the air, and the whole 

 bound up to secure it from external injury. After a 

 few years, the branch was cut through transversely. 

 The cylinder of bark was found lined with layers of 

 new wood, whose number added to those in the wood 

 from which it had been stripped, made up the number 

 of rings in the branch above and below the experiment. 

 For an account of this experiment I am indebted to 



