FOSSIL FLORA. 771 



maybe drawn up as follows: Annual ring present, but faintly demarked; 

 wood cells long, narrow, sharp-pointed, thin-walled; ducts very numerous, 

 occupying about one-half of the area, in radial rows of from 2 to 10, 

 pitted, the pits small, round; medullary rays numerous, of short, thin-walled 

 cells, rectangular or irregular in transverse section, arranged in 2 to some- 

 times 4 vertical rows of approximately 10 to 30 cells each. 



Habitat: Specimen Ridge, near head of Crystal Creek, Yellowstone 

 National Park; collected by F. H. Knowlton, August 22, 1887. 



QuERCINIUM LAMARENSE U. Sp. 

 PL CXVIII, fig. 5; PI. CXX, fig. 2; PL CXXI, figs. 1, 2. 



Transverse section. — Annual ring present, but very faint ; consisting of but 

 1 or 2 rows of thickened cells. In the succeeding spring wood the ducts 

 are much larger, thus making the ring visible to the naked eye. 



Ducts numerous, scattered, most abundant in spring and summer 

 wood; all single — that is, not contiguous. They are almost perfectly 

 circular, being very slightly elongated radially. They are large, though 

 not remarkably so for the genus; the larger ones ranging in diameter 

 from 0.16 to 0.23 mm., the smaller being about 0.20 mm. The very 

 smallest ducts are 0.05 mm. in diameter, and the more common of the 

 small ones are 0.10 or 0.12 mm. in diameter. None of the ducts are 

 arranged in notable radial rows. 



The wood cells are in distinct radial rows, and are large and thick- 

 walled. In most the lumen is nearly obliterated. The average size of the 

 wood cells is 0.02 mm. 



The medullary rays are neither very numerous nor conspicuous. They 

 are mainly only 1 cell broad, with an occasional wide one of 20 or more 

 cells, as will be described under the tangential section. Some of the single- 

 celled rays pass for a considerable distance among the ducts, but by far the 

 larger number lie between two ducts (see fig. 1 of PI. CXXI). 



Radial section. — The only sections available in this direction were, unfor- 

 tunately, from poorly preserved portions of the specimen, and do not show 

 the structure clearly. The wood cells, so far as can be made out, are very 

 loner, and, as shown bv the transverse section, have thick walls The rays 



O r J ' J 



