78 R. F. Field — Studies of Muir Glacier. 



late and early wood, although they are represented in the draw- 

 ing only in the latter. 



A specimen of recently grown spruce was obtained by Mr 

 Reid from Alaska,^] and I have compared it carefully with the 

 preceding and find that the two agree in every structural detail. 

 Figures of transverse and longitudinal sections of the recent wood 

 are not given, since they Avould be merely repetitions of figures 

 4 and 5. The size and shape of the medullary rays are essentially 

 the same, and the average number of rays joer square millimeter 

 of section is the same in the two specimens. Resin canals are 

 occasionally seen in the midst of a thickened medullary ray in 

 the modern wood, and while I have not observed them in the 

 buried-forest wood, yet I have no doubt that they would be 

 found by persistent sectioning. Transverse sections of the new 

 wood show the same differentiation between the earlier and later 

 cells of the annular ring. The modern wood is several shades 

 lighter than the old, and the brownish tinge of the grain is due 

 to the color of the medullary tissue. The conclusion Avould be 

 warranted, upon the evidence above given, that the wood taken 

 from a forest at one time buried under glacial deposits in Alaska 

 and submitted to me for examination by Mr Reid is si3ecifi- 

 cally identical with that of the Alaskan spruce (Abies sitkensis or 

 A. menziesii) which grows 'in the neighborhood of the glaciers of 

 Alaska to-day, provided that microscopical examination of the 

 wood alone could be relied ujjon for the determination of species 

 of coniferous trees. Unfortunately for the student of this subject, 

 the structure of the wood must be supplemented by other char- 

 acters before the species can definitely be settled. The preced- 

 ing observations can, however, be said to render quite probable, 

 at least, the conclusion intimated above. 



Adelbert College, March 14, 1891. 



[*] This was sent to me from Juneau by Reverend Eugene S. Willard. 

 H. F. R. 



