BOTANY. 31 



In the spring season a mucilage is formed between the 

 bark and wood, called the camb, or cambim. Towards 

 the decline of the year it becomes considerably indurated, 

 and separates itself into two concentric hollow cylinders 

 of very different thicknesses. The thinner one is attach- 

 ed to the bark and forms its inner membrane. The thick 

 one is attached to tlie wood, and becomes the outer layer 

 of the wood for the next year. 



It is on this account that those trees, which long retain 

 their expanding cuticles, present to our land surveyors 

 those paradoxical magic-like marks. A beach tree, for 

 example, if lettered or figured with a board-marker, will 

 present these marks twenty or thirty years afterwards 

 both on the cuticle and on the wood of the year when 

 marked ; while the intervening layers are sound and 

 without a scar. These interposed woody layers, origin- 

 ating in mucilage annually deposited between the bark 

 and w r ood, gradually separate the marked bark and cuti- 

 cle from the marked wood; while they grow between 

 these marks and become continuous? 



