XLIV] PROTOCEDROXYLON 237 



Annual rings well marked ; bordered pits on the radial walls of 

 the tracheids in 1 — 3 rows; in the Spitzbergen wood these are 

 from 20 to 24/* in height, dimensions larger than in recent Arau- 

 carineae, and in the type-specimen the pits are always contiguous, 

 more or less flattened and alternate — that is Araucarian ; in the 

 English specimens the pits when in a single row are often separate 

 and circular but equally often contiguous. Jeffrey points out 

 that the alternate pits when in more than one series are less 

 crowded than in Araucarian wood. There are no Sanio's rims. 

 The medullary rays are uniseriate and characterised by Abietin- 

 eous pitting on the horizontal and tangential walls ; on the radial 

 walls there are 1 — 3 circular, apparently unbordered, pits in the 

 field. Xylem-parenchyma is practically absent. An interesting 

 feature is the abundance both in the Spitzbergen and Yorkshire 

 material of tyloses in many of the tracheids, a feature occasionally 

 met with in recent Conifers^ as in some other fossil species. The 

 pitting of the tracheids in the type-specimen may be described as 

 exclusively Araucarian, but in the English specimens separate 

 pits also occur though on the whole the Araucarian type is domi- 

 •nant. The pitting of the medullary rays is on the other hand 

 definitely Abietineous. The American authors, particularly Miss 

 Holden^, consider that the absence of Sanio's rims sufiices to tip 

 the balance on the Araucarian side. On most of the tracheids 

 the crowding of the pits precludes the occurrence of Sanio's rims 

 and in other cases their absence is not necessarily an original 

 feature. Abietineous pitting is recorded by Jeffrey in the cone- 

 axis of an Agathis and it has also been found in Araucaria; but 

 in the Araucarineae it is very exceptional: its occurrence as a 

 constant feature in Protocedroxylon may be regarded as an indica- 

 tion of Abietineous relationship. No substantial assistance is 

 afforded by impressions in Spitzbergen rocks: the abundance of 

 Elatides is consistent with the occurrence of Araucarian wood, blit 

 impressions of Abietineous Conifers afford at least as strong an 

 argument in favour of the occurrence of Abietineous wood. 



Protocedroxylon scoticum (Holden). This species, described by 

 Miss Holden^ under the generic name Metacedroxylon from Coral- 

 lian beds on the Sutherland coast of Scotland, is founded on a piece 

 1 See page 178. 2 Holden, R. (15). 



