XLIV] 



PROTOPICEOXYLON 



233 



and narrow; several oval or circular spaces are conspicuous in 

 transverse section, some being true canals and others the result 

 of decay. There are 2 — 3 opposite rows of bordered pits on the 

 radial walls of the tracheids. Partially destroyed rows of resin- 

 parenchyma occur which probably belong to secretory canals. 

 The uniseriate and comparatively deep medullary rays, 20—30 

 cells, are characterised by rather thick and pitted horizontal and 



Fig. 728. Protopiceoxylcm arcticum. 

 (Cambridge Botany School.) 



Fig. 729. ProtopiceoxyhnEd- 

 wardsi. Longitudinal view 

 of the thick- waUed, pitted, 

 epithelial cells of the resin- 

 canals. (After Stopes.) 



vertical walls (fig. 728) ; 4 — 5 small simple pits occur on a few of 

 the cells and on the upper and lower edges of some of the rays are 

 empty elements of unequal breadth which in all probability are 

 ray-tracheids. The wood agrees in the presence of vertical 

 canals only and in the structure of the medullary rays with Proto- 

 piceoxylon exstinctum Goth. In Gothan's species there are 2 — 4 

 bordered pits in the field, but the absence of a border in 

 the Franz Josef Land wood may be a consequence of imperfect 

 preservation. 



