CORDAITES 199 



Bordered pits in one row, compressed. 



Ray cells (tangential) broad, round, or squarish. 



4. C. recentium. 

 Bordered pits in 1-3, chiefly 2, rows. 



Ray cells (tangential) broadly oval. 

 Ray cells about 31-57 p. broad. 



5. C. hamiltonense. 

 Ray cells about 28-37 p. broad. 



Pits on the lateral walls of the ray cells about 1-4 per tracheid. 



6. C. illinoisense. 

 Ray cells (tangential) oval or round. 



Pits on the lateral walls of the ray cells i-S, chiefly 2-3, per 

 tracheid. 



7. C. materioide. 

 Ray cells not determinable. 



8. C. annulatum. 

 Bordered pits in 2-5 rows. 



Ray cells (tangential) oval or oblong. 



Pits on the lateral walls of the ray cells 2-4, chiefly 4, per tracheid. 



9. C. ouangondianum. 



Pits on the lateral walls of the ray cells 4-10, chiefly 6, per tracheid. 



10. C. acadianum. 

 Ray cells (tangential) broad or squarish. 



Pits on the lateral walls of the ray cells 2 per tracheid. 



11. C. ohioense. 

 Ray cells (tangential) oval or round. 



Pits on the lateral walls of the ray cells 1-5, chiefly 1-2, per 



tracheid. 



12. C. materiarium. 



Bordered pits in 5 rows. 



13. C. Hallii. 



1. C. pennsylvanicum, Dn. 



Transverse. Tracheids 44 x 44 /A broad, the walls 6.7 p. thick. Growth rings 

 present, the summer wood about 8 tracheids thick, the tracheids about 

 12.5 p. radially, the walls 3.1 p. thick. Resin passages and resin cells 

 wanting. 



Radial. Ray cells all of one kind, conspicuously but gradually narrower 

 toward the ends, equal to about 3 tracheids ; the lateral walls with 

 round or oval pits, about 2-3 per tracheid. 



Tangential. Rays medium, broad, the cells round or transversely oval, vari- 

 able, 25-31 p. broad. 



The Carboniferous at Pittsville, Pennsylvania. 



