762 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



The medullary rays are composed of 1 , or in some cases of a par- 

 tially double, series of 2 to about 25 superimposed cells. They are large 

 and quite thick walled. The average number of cells in each ray is 

 about 12. 



This species is closely related to the living Sequoia sempervirens Endl., 

 more closely than any other fossil species with which I am familiar. They 

 are hardly to be separated by any Avell-defined characters. The living 

 wood has the same clearly marked annual rings, resin cells, partially double 

 rays, and pits on the wood cells. The medullary rays in the living wood 

 are provided with numerous round pores or markings. These seem to be 

 absent from the fossil specimens, but, as_ already related under the diagnosis, 

 the fossil is not well preserved in the radial section and they may have 

 been present there when it was living. The dimensions of the various 

 elements are much the same in the living and fossil specimens, thus leaving 

 no doubt as to their close affinity. 



In size of trunks these species are also similar. The largest trunks 

 observed in the Yellowstone National Park belong to S. magnified. They 

 range in size from 4 to 10 feet in diameter, one of the largest being shown 

 on PI. CV. This is 26£ feet in circumference and stands upright on the 

 hillside. It is 12 feet high, and represents the base of the trunk, as the 

 large roots are well preserved. Their height is of course unknown, but one 

 was fortunately prostrated before fossilization (PI. CVIII), and is 40 feet 

 long, with no apparent diminution in diameter. It is altogether likely that 

 they may have been equal in height to some of the living representatives. 



I have thought best to give this fossil species a name different from 

 that of the living tree, notwithstanding the fact that they are evidently so 

 closely related. The fossil comes from a locality remote geographically 

 from the living redwood, and, moreover, from a horizon that, although com- 

 paratively recent, is so ancient as to make it extremely improbable that 

 the type has actually been living for so long a period. There can, hoAvever, 

 be no doubt that the living redwood is the direct descendant of this 

 remarkable tree that was once so abundant in the Yellowstone National 

 Park. 



Habitat: Specimen Ridge, Fossil Forest at head of Crystal Creek, 

 Fossil Forest on Cache Creek, etc.; collected by F. H. Knowlton, August, 

 1887-August, 1888. 



