1 64 ANATOMY OF THE GYMNOSPERMS 



which constitute the source of decay. It is not our purpose to 

 discuss the particular mode of action of these organisms at the 

 present moment, since that is more appropriately reserved for 

 a subsequent chapter, but a few concrete examples will serve to 

 indicate somewhat more exactly the relative durability of certain 

 species under widely different conditions. 



One of the most instructive examples to which our attention 

 has been drawn, not only because of the very perfect state of 

 preservation but also because of the great length of time the 

 wood has resisted the action of decay, is to be found in Sequoia 

 Penhallowii, as recorded by Jeffrey (25). The wood in question, 

 representing a large fragment of a tree at least six feet in 

 diameter, presents the external aspects of a recently cut piece 

 taken from an existing tree. It is of Miocene age, and was 

 obtained from the Sierra Nevada Mountains on the line of the 

 Central Pacific Railway, under sixty feet of conglomerate, where 

 it was located in the auriferous gravels. No difficulty was ex- 

 perienced in making sections of this wood for the microscope, no 

 more than would be encountered in wood taken from an exist- 

 ing tree, since it was very slightly silicified. A microscopic 

 examination shows the structure to be most beautifully and per- 

 fectly preserved in all its details ; while several beautifully pre- 

 pared sections, for which I am indebted to the courtesy of 

 Dr. Jeffrey, also make it evident, from the complete absence of 

 fungus mycelia, that these latter had not found their way into 

 the tissues at any time during the long burial of the tree. The 

 special interest of this wood centers in the fact that, so far as I 

 am aware, there is no other example of an uninfiltrated and 

 unaltered wood from so ancient a formation. 



More recent Tertiary strata afford numerous examples of a 

 similar character. The Pleistocene in particular has furnished 

 many instances of the most perfect conditions of preservation, 

 chiefly of woods which, under ordinary circumstances, would be 

 regarded as "durable." In 1898 Professor A. P. Coleman of To- 

 ronto obtained from the Pleistocene clays of the Don valley, at that 

 place, a specimen of the common red cedar (Juniperus virginiana) 



