XLIV] CEDROXYLON 217 



alternate and form stellate groups. The medullary rays, reaching 

 a depth of 30 cells, show very clearly the Abietineous pitting and 

 there are 4 5 simple circular pits in the field. The occasional 

 occurrence of single large pores in the field would seem to be due, 

 at least in part, to the destructive action of fungi. Xylem- 

 parenchyma occurs in the summer-wood. The structure agrees 

 with that of the wood of Cedrus, Pseudolarix, and Tsuga; the 

 Abietineous features are relatively more conspicuous than in 

 Cedroxylon transient in which the tracheal pitting is more Arau- 

 carian. 



Cedroxylon maidstonense S topes. 



In this wood 1 , from the Lower Greensand of Kent, the rings 

 of growth are well marked ; the bordered pits on the radial walls 

 of the tracheids are usually uniseriate and Sanio's rims are dis- 

 tinctly preserved. Xylem-parenchyma is absent or very rare and 

 there are no resin-canals. The medullary rays are seldom deeper 

 than 10 cells; there are 4 6, or occasionally more, oval or 

 circular pits in the field and some have a slit-like pore and are 

 bordered ; pits are clearly shown on the tangential walls of the 

 ray cells. 



Cedroxylon pottoniense Stopes. 



This species 2 of the same geological age, from Potton in Bedford- 

 shire, differs from C. maidstonense in the comparative abundance 

 of xylem-parenchyma : the medullary-ray cells show very clearly 

 the Abietineous type of pitting. 



Cedroxylon blevillense Lignier. 



In this species from the gault of Bleville (Seine-Inferieure) 3 

 the tracheal pits are usually uniseriate and separate but if in two 

 rows they may be either opposite or alternate. The pits in the field 

 are small, numerous, and have an oblique pore (fig. 723, C). The 

 tangential walls of the ray cells are sometimes pitted. There is 

 no resiniferous parenchyma. The characters afford another illus- 

 tration of the impossibility of drawing any clearly defined line 

 between Cedroxylon and allied generic types. 



1 Stopes (15) p. 149, PL xn. text-figs. 4143. 2 Ibid. p. 154, text-fig. 44. 



3 Lignier (07 2 ) p. 267, PL XVIIT. figs. 1517; PL xxi. fig. 66; PL xxn. fig. 72; 

 PI. xxiii. fig. 87. 



