XLIV] XENOXYLON 241 



parenchyma but tylose-like cross-walls occur in some of the xylem 

 elements. 



The nature of the pitting led Kraus^ to include Cramer's 

 species in Araucarioxylon and Miss Holden^, who records this 

 species from the Yorkshire coast, regards the absence of Sanio's 

 rims as evidence of Araucarian affinity. The medullary-ray 

 pitting is, however, very different from that in recent Araucarineae 

 and the absence of Sanio's rims may well be a natural consequence 

 of the crowded arrangement of the tracheal pits. 



Xenoxylon phyllocladoides Gothan. 



This species, founded on material from the Bathonian of 

 Russian Poland*, differs from X. latiporosum in the not infrequent 

 occurrence of separate and circular pits on the tracheids : in it are 

 included specimens from Liassic rocks at Gallberges near Salzgitter 

 in Germany described by Conwentz* as Araucarioxylon latiporosum 

 (Cram.) and, with some hesitation, Cupressinoxylon Barheri Sew.* 

 from the Yorkshire coast. The tracheal pits are uniseriats, 

 flattened or separate and circular (fig. 730, A), or in two rows, 

 generally though not invariably opposite ; they vary in size from 

 22 X 30 /i to 24 X 36 /x; the medullary rays are generally less than 

 10 cells deep and in pitting agree with those of the type-species. 

 This species is recorded from Poland, Spitzbergen, King Charles 

 Land*, Yorkshire, and Germany. 



Though similar to Araucaria and AgatJiis in the flattened con- 

 tiguous pits, Xenoxylon differs in the elliptical form of the border 

 and pore, also in the occurrence of separate and circular pits and 

 in the occurrence of opposite pairs. In the form of the pits on the 

 tracheids Xenoxylon resembles the Palaeozoic species Dadoxylon 

 protopityoides Fel.'' and pits of similar form occur in the wood of 

 the recent Magnoliaceous plant Drimys Winteri^. From the 

 Abietineae the genus is distinguished by the restriction of the 

 medullary-ray pitting to the radial walls, though the large pores 



1 Kraus in Schimper (72) A. p. 384. 



2 Holden, R. (14) p. 536, PI. xxxix. figs. 5, 6. 



' Gothan (06^) p. 4,54, fig. 4; (10) p. 36, PI. vi. figs. 9, 10, etc. 



< Conwentz (82) p. 170 



s Seward (04) B. PI. vii. ; Holden, R. (14) p, .53.5. 



1 Gothan (08^) p. 10, figs. 3—9. 



' Fehx (86) A. PI. v. fig. 4. « Groppler (94) Pis. I., il. 



S TV 16 



