CUPRESSOXYLON 



12. * * C. comanchense, Penh. 



239 



Transverse. Tracheids in regular, radial rows, rounded, very uniform, 44 x 

 44 //, broad, the walls 12.5 /u. thick. Growth rings prominent, about 10 

 in a radial extent of 22 mm. ; the summer wood thin, composed of 2-4 

 rows of tracheids, the latter about 22 p. wide, the walls 12.5 ^ thick. 

 Resin passages and resin cells wholly wanting. Worm burrows are fre- 

 quent and show copious exudation of resin, which has often preserved 

 the adjacent structure from decay. 



Radial. Ray cells of one kind only, straight ; the upper and lower walls 

 thin and not pitted ; the terminal walls thin, not pitted, chiefly curved ; 

 the lateral walls with oval, bordered pits, about 1-2 per tracheid, the 

 oblong or broadly lenticular orifice nearly as long as the pit ; the cells 

 equal to about 4 tracheids. Bordered pits round, large, 1 9 /x broad; 

 in i or sometimes 2 rows, the orifice round. 



Tangential. Rays i -seriate, the cells thin-walled, round, 19 p. broad. 



Material silicified. Specimens represented by small fragments of a stem. 

 Comanche Cretaceous (?) northwest of Ashland, Clark County, Kansas 

 (Prosser). 



13. ** C. pulchellum, Knowlton 



" Transverse. The pith is well preserved and consists, when viewed under 

 the microscope, of numerous large, rather thick-walled cells with an 

 elliptic or nearly circular outline. The larger cells, which have a 

 diameter of .05-. 08 mm., occupy the center, from which they de- 

 crease in size and pass more or less gradually into the medullary 

 rays. The rays are very numerous and pass in nearly a straight line to 

 the circumference. No trace of bark remains. The tracheids are 

 arranged with great regularity in radial rows, and are remarkable for 

 their small size, particularly where they are in contact with the pith. 

 As the medullary rays diverge, new layers of tracheids are intercalated 

 to fill up the space. The line of demarcation between the annual 

 layers is generally well defined, the fall wood consisting of 5-8 com- 

 pressed cells in each radial row. The spring wood consists of much 

 larger cells, which have a diameter of .025-. 035 mm. These cells are 

 more nearly hexagonal than the others, and, decreasing gradually in 

 size, pass into the next ring of fall wood. 



" Radial. In this section the tracheids are seen to be long and provided 

 with a single longitudinal row of bordered pits, which have an average 

 outer diameter of .01 7-. 021 mm. The inner circle of the pits is rather 

 small, with a diameter of .005-. 006 mm. The medullary rays are 

 cut up into comparatively short cells, each one covering the space 

 of five or six of the tracheids ; markings seem to be absent from 

 the walls of the rays, but the real state of affairs may be masked by the 

 petrifying material, which has evidently somewhat disorganized the 

 original structure. The resin ducts (cells) are numerous. These con- 

 sist of a chain of short, regular cells, which are slightly constricted at 

 the ends. The individual cells are .08-. 15 mm. in length, and are 

 usually filled with minute globules of darker matter. 



