CAXADIAX FlHllElilES FXPEDITIOX. 191 ',-15 



85 



The inner structure of the scale tlius plays no part in the formation of the pic- 

 ture presented by the visible system of annual rings. It is possible, however, by par- 



Plate III. 



IG. 3 



ticular means, to bring out another system of annual rings, located in close relation 

 to those of the outer surface, yet altogether different from these. In order to com- 

 prehend the genesis of this inner system, it will be necessary to have some idea as to 

 the internal structure of the scale as a whole. This may be arrived at by various 



