PITYOXYLEN 



351 



coarsely pitted ; the terminal walls rather thin and locally thickened ; 

 the lateral walls with round, bordered pits about i 1.5 /A broad, chiefly 

 i, or sometimes 2, per tracheid, the orifice lenticular, diagonal. Wood 

 parenchyma resinous ; the cells cylindrical, 2-several times longer 

 than broad, the radial walls with rather small pits. 



Tangential. Ordinary rays resinous, numerous, variable, low to high, 1-2 

 seriate, or sometimes 3-seriate, and approximating to the fusiform 

 type through various gradations, but always devoid of resin canals ; 

 the usually large cells very unequal and very variable, ranging from 

 oblong to oval, round or transversely oval, the strong inequality and 

 variability giving a marked irregularity of form to the ray as a whole. 

 Fusiform rays rather numerous, low to high, the central tract occupied 

 by i rather small resin canal devoid of thyloses, but with small and 

 thick-walled epithelium cells ; the terminals short or sometimes un- 

 equally prolonged to considerable length. Wood parenchyma resinous, 

 the short-cylindrical cells with thin walls and bearing pits on all their 

 walls. Rudimentary spirals may be seen in the tertiary layer of many 

 of the tracheid walls. 



Cretaceous (?) of Third Cliff, Scituate, Massachusetts. Material in the 

 form of lignite (Bowman). 



