192 CONIFERALES [CH. 



single row, rarely double in the roots, free and circular in branches, 

 often contiguous and compressed in roots ; tangential pits common. 

 Medullary rays usually uniseriate, 1 16 cells deep, pits confined 

 to the radial walls, usually 1 but sometimes 2 4 oval and oblique 

 pits in the field. Resin-canals absent; resin-parenchyma in 

 vertical rows, abundant and scattered. The pith consists of pitted 

 parenchymatous cells separated by intercellular spaces ; in the roots 

 the rows of tracheids pass directly into the cells of the pith; in 

 the branches they terminate in small groups of cells irregularb 

 arranged. 



Cupressinoxylon McGeei Knowlton. 



This is one of several species from the Potomac lignites included 

 by Knowlton 1 in Cupressinoxylon. The annual rings are well 

 marked ; the tracheids have 2 3 rows of opposite and circular pits 

 on the radial walls and small bordered pits are abundant on the 

 tangential walls. The uniseriate medullary rays, 2 49 cells deep, 

 have 1 2 oval apparently simple pits in the field and resin- 

 parenchyma is abundant. Gothan 2 has described some wood of 

 Lower Cretaceous age 3 from King Charles Land as Cupressinoxylon,, 

 cf. C. McGeei, agreeing with Knowlton's type in the medullary-ray 

 pitting; there are 2 4 simple pits in the field, elliptical and hori- 

 zontal ; an indication of a border was seen in some of the pits in 

 the region of the summer- wood, but the general absence of a border, 

 if an original feature, is a difference between this wood and that 

 of recent genera included in Cupressinoxylon. There is no Abie- 

 tineous pitting on the ray cells. 



The species Cupressinoxylon luccombense described by Dr 

 Stopes 4 from the Lower Greensand of the Isle of Wight closely 

 resembles C. vectense, but it has stone-cells in the pith, the tracheids 

 are larger and there are usually 3 4 pits in the field in place of 1 

 or sometimes 2 3 in C. vectense; moreover in the latter species 

 the pits of the ray cells are more uniform in size. 



1 Knowlton (89 2 ) p. 46, PI. n. fig. 5; PL in. figs. 15. 



2 Gothan (07 2 ) p. 19, fig. 10. 



3 Gothan speaks of the King Charles Land fossils as Jurassic, but the beds have 

 since been shown to belong to the Cretaceous system. See Burekhardt (11). 



4 Stopes (15) p. 180, text-figs. 5153. 



