XLIV] PITYOXYLON 225 



opposite but stellate groups also occur as in Cedroxylon transiens 

 Goth. (fig. 723, A) and several other species. The uniseriate 

 medullary rays reach a depth of 30 cells : there are usually 2 — 4 

 oval or circular pits in the field. 



A similar type of stem is represented by Pityoxylon Nathorsti^ 

 (Conw.) from the Lower Cretaceous of Sweden. 



Pityoxylon Sewardi Stopes. 



This species^ is founded on a petrified branch, not less than 18 

 cm. in diameter, from the Lower Greensand of Kent. It exhibits 

 the usual features characteristic of the genus ; the wood contains 

 horizontal and vertical canals with thin-waUed epithelial cells. The 

 medullary rays are larger and more abundant than in most Coni- 

 ferous woods and horizontal tracheids (fig. 726, tr) occur inter- 

 spersed with the parenchymatous cells, c, as well as on the upper 

 and lower margins, an arrangement in which the fossil bears a 

 striking resemblance to the recent species Pinus monticola^. 



Pityoxylon Benstedi Stopes. 



In this Lower Greensand species* from Kent the resin-canals 

 often contain tyloses as in P. Nathorsti Conw. and the epithelial 

 cells have very thick walls, a feature suggesting comparison with 

 the genus Larix. The medullary rays show well-marked Abie- 

 tineous pitting (fig. 727, a) and ray-tracheids (rt) occur. Rims of 

 Sanio are shown in fig. 727 between the circular bordered pits, 

 tr. The difference between the tracheal and ordinary parenchy- 

 matous elements of the rays, as represented in fig. 727 from a 

 drawing by Dr Marie Stopes, is not very clearly defined and in the 

 upper ray shown in the figure part of a tracheid is seen abutting 

 laterally on parenchymatous ray cells, the only difference between 

 them being in the form of the pits, a criterion which is largely 

 dependent for its value on the state of preservation. Dr Stopes is 

 inchned to regard this species as most nearly allied to Larix. 



Pityoxylon statenense Jeffrey and Chrysler. 



A species from the Middle Cretaceous of Staten Island^ found 

 in association with the short shoots described by Jeffrey and 



1 Conwentz (92) p. 13, Pis. i. — lu., vi., vn. 



2 Stopes (15) p. 95, Pis. iv., v. text-figs. 2.3, 24. » Ibid, text-fig. 25, p. 103. 

 « Ibid. (15) p. 105, Pis. v.— VII. text-figs. 26, 27. 



* Jeffrey and Chrysler (06). 



S. IV 15 



