t 



i 



XLIV] PITYOXYLON 219 



but sometimes alternate though not contiguous. The medullary 

 rays, 5 12 or rarely 20 cells deep, are imperfectly preserved. 

 Another species, C. Yendoi St. 1 and Fuj. from the same locality is 

 also founded on material that is insufficient for accurate deter- 

 mination. Sporadically occurring resin-ducts are regarded as 

 traumatic. 



Among Tertiary species reference may be made to Cedroxylon 

 affine Kraus 2 from Sicily, without resin-parenchyma and charac- 

 terised by usually two large simple pits in the field ; C. Hoheneggeri 

 Felix 3 from the Eocene of Moravia figured by Schenk as from 

 Cretaceous strata ; C. Hermanni Sch. 4 , an incompletely described 

 species from Assam, probably of Tertiary age. 



VII. PITYOXYLON. Kraus. 



Kraus 5 included in this genus some of the species previously 

 referred by Goeppert to Pinites ; others he assigned to Cedroxylon. 

 Pityoxylon is distinguished from Cupressinoxylon and Cedroxylon 

 by the normal occurrence of resin-canals in the wood and by the 

 presence of horizontal tracheids in some of the medullary rays. 

 Within the limits of the genus the following differences occur in 

 he characters of the medullary rays and the resin-canals : the 

 walls of the ray-tracheids are smooth or provided with dentate 

 ingrowths ; the pits on the medullary-ray cells are large and simple 

 or smaller and apparently bordered, and there may be one or 

 veral pits in the field ; the parenchyma of the resin-canals has 

 thin or thick walls. As generally employed Pityoxylon includes 

 species exhibiting anatomical features met with in Pinus, Picea, 

 Larix, Pseudotsuga, and some other Abietineae. Gothan 6 makes 

 use of two generic names, Piceoxylon and Pinuxylon, to denote the 

 possibility of more precise comparison with recent types than is 

 implied by Kraus's more comprehensive term. Piceoxylon is 

 characterised by thick- walled epithelial cells lining the resin-canals, 

 by small pits in the ray cells, spiral tracheids in the summer- wood, 

 the absence of teeth in the ray-tracheids, clearly marked Abietineous 



1 Stopes and Fujii (10) PL iv. figs. 2426. 



2 Kraus (83). 3 Felix (82) p. 268. 



4 Schenk (82 2 ) p. 355. 5 Kraus in Schimper (72) A. p. 377. 



6 Gothan (05) p. 102. 



