772 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



t'oriu high phite.s <it' cells, the exact length of which can not be determined 

 with satisfaction. If there were markings on the rays they can not be seen; 

 neither can the markings on the ducts be observed. 



Tangential section. — Tliis section sliows nuiclibettcr under the microscope 

 than the radial uiic. 



The ra}s are found to be of two distinct kinds: The most numerous 

 are only 1 cell Inroad and from 10 to 25 cells high, the individual cells 

 being thin-walled and oblong in shape. At scattered intervals are very 

 broad rays composed of 10 to 20 rows of cells and extending for long 

 distances through the section (see fig. 2 of PI. CXXI). These broad rays 

 are often somewhat cut by wood cells passing diagonally through them 

 (see fig. 2 of PI. CXXI). This does not, however, interfere with the ray 

 as a whole, which is clearly demarked from the small rays of a single 

 series of superimposed cells. The individual cells of the large rays are 

 neai'ly circular in cross section, or more or less 6-sided by mutual pressure. 

 They are also thiu-walled. 



Associatefl with the small rays is usually a layer or two of short-celled 

 tissue or series of parenchymatous cells. Except for there being shorter 

 cells they are not to be distinguished from the ordinary wood cells. 



The ducts show clearly enough in fhis section, but they are not well 

 enough preserved to permit the markings on the wnlls to be made out. It 

 would seem that the walls were pitted, but this is largely .surmised. 



A considerable luiniber of species of Quercinium,' or oak wood, in a 

 fossil state, have been described from yari(ius parts of the world. Wood 

 of this kind is readily distinguished by the large isolated ducts and the two 

 kinds of medullary rays. 



The species under consideration resembles a number of described 

 forms, but they are all fi-om the (Jld World, and are readily distinguished 

 from it. 



This species is closely allied to Quercinhim knoivUniil Felix, and may 

 possibly be the same, bat as Felix's species is not fully illustrated it is 

 difficult to be positive. Q. lamarense seems to differ in the shape and size 

 of the large ducts, l)ut it will need a careful comparison of the sections to 

 be positive. For the pi-esent, at least, they may remain distinct. 



Habitat: Specimen Ridge, Yellowstone National Park; specimen from 



' Fifteen species auil vaiii-ties. 



