FOSSIL FLORA. 765 



and are rather small. They are so obscure that it is impossible to make 

 trustworthy measurements. 



The medullary rays, as seen in this section, are composed of long, thin- 

 walled cells, and so far as can be determined they are without pits or other 

 markings. 



Tangential section. — This section (PI. CXVIII, fig. 2) shows the structure 

 very plainly. The medullary rays are abundant and always in a single 

 series, except the large compound ones. The number of cells in each ray 

 varies from 2 to 10 or 12, the average number being about 6. The com- 

 pound rays inclosing the resin ducts are rather small, with three rows of 

 cells in the middle portion. No markings can be made out on the wood 

 cells in this section. 



This species is very closely allied to the one preceding, and should 

 perhaps be referred to it. The main points of difference are the following: 

 Narrower annual rings; smaller resin ducts, that are occasionally found in 

 the summer wood; smaller wood cells throughout; smaller and shorter 

 compound medullary rays; ordinary rays always in a single series of 2 to 

 12 cells (average 6) instead of from 2 to 30 or more (average 12). 



Habitat: Specimen Ridge, Fossil Forrest, near head of Crystal Creek; 

 collected by F. H. Knowlton, August, 1887. 



Laurinoxylox pulchrum n. sp. 



Pis. CXVI, CXIX, figs. 3-5; PI. CXX, fig. 1. 



Transverse section. — Annual ring very distinct to the naked eye, 2 to 4 mm. 

 broad. The demarcation between the rings results from 10 or 12 layers 

 of thicker- walled cells, representing the late fall wood, and from the greater 

 abundance of ducts in the immediately following spring wood. 



The wood cells are small and arranged in serial rows except in the 

 vicinity of the ducts, where they are somewhat irregular (see fig. 1 of PI. 

 CXX). Surrounding the ducts, and sometimes filling the remainder of the 

 space between rays, the cells are larger and not so completely seriated. 

 The ordinary wood cells are about 0.01 mm. in diameter, and those near the 

 ducts 0.015 or 0.02 mm. There is an occasional row of the large-sized 

 wood cells along a ray, as in fig. 1 of PI. CXX. 



The ducts are very plainly shown in this section. At least half of 

 them are single and nearly or cpxite circular in section. Of the remainder, 



