200 ANATOMY OF THE GYMNOSPERMS 



2. C. Clarkei, l)n. 



Transverse. Growth rings obscure or entirely wanting. The tracheids about 

 41 x49 /LI broad, their walls 12.5 p. thick. 



Radial. Bordered pits numerous throughout the tracheids, in 2-3, more 

 rarely in 4, rows. The elements of the medullary rays of two kinds ; the 

 parenchyma cells thin-walled and devoid of pits, about equal to 3 

 tracheids; the ray tracheids long, interspersed, and bearing on their 

 lateral upper and lower walls numerous crowded, bordered pits. 



Tangential. Rays very variable, commonly i -seriate but sometimes 2-seriate 

 in part ; the tracheids usually distinguished by their narrow form and 

 pitted walls. 



Hamilton Group, Ithaca, New York. 



3. C. Newberryi, (Dn.) Knowlton 



Transverse. Tracheids about 44 x 55 p., the walls about 12.5 p,, thick. 



Radial. Ray cells resinous and starch bearing, long and narrow, about equal 

 to 3-7 tracheids, the ends conspicuously narrower; the pits on the 

 lateral walls 3-6, chiefly 4, per tracheid, the slitlike orifice nearly the 

 full diameter of the pit. Bordered pits numerous, round, about 9.3 p. 

 broad, distributed in radially disposed groups of about 6-13; the ori- 

 fice diagonal, nearly the diameter of the pit. 



Tangential. Rays of medium height, i-, 2-, or rarely 3-seriate in part ; 24-55 

 p. broad, the oval or round cells all thin-walled. 



Hamilton Group (Middle Devonian) of Ohio (Newberry) ; Carboniferous of 

 Ohio (Claypole). 



4. C. recentium, Dn. 



Transverse. Tracheids 47 x 53 p, broad, the walls much reduced by decay. 



Radial. Ray cells all of one kind, about equal to 2 tracheids ; the lateral 

 walls with round pits about i (?) per tracheid ; the cells conspicuously 

 narrower at the ends. Bordered pits in a single row, compact, large, 

 compressed, and transversely oval or oblong, 15.6 x 22 p., the orifice 

 very variable from oblong to round, often eccentric, but typically round 

 and central. When distant the pits are round and smaller. 



Tangential. Rays medium, i-seriate or 2-seriate, the very broad cells 41 p., 

 thin-walled, round, and squarish. 



The Permian or Permocarboniferous of Prince Edward Island. 



5. C. hamiltonense, Penh. 



Transverse. Tracheids very variable, growth rings obscure. 



Radial. Structure of the medullary rays not determinable. Bordered pits 



hexagonal, in 2 rows throughout. 



Tangential. Rays numerous and variable, 31-57 P- broad; the cells very 

 'variable in form and size, thin-walled, often broader than high, chiefly 

 i-seriate, often more or less 2-seriate. 



Genesee shales (Hamilton Group) of Ontario County, New York. 



