232 CONIFERALES [CH. 



Prolopiceoxylon exstinctum shows the following characters: 

 annual rings well marked ; vertical resin-canals occur in the wood 

 but there are no canals in the medullary rays except a few of 

 unusually large diameter in wounded areas; there is no xylem- 

 parenchyma apart from the resin-canals. Tracheids with 1 2 

 rows of bordered pits on the radial walls, separate and circular, 

 also contiguous and flattened, opposite, or sometimes alternate : 

 in the occurrence of the Araucarian type of pitting on some 

 tracheids this species agrees with several types of Mesozoic wood. 

 Medullary rays uniseriate, characterised by well-developed Abie- 

 tineous pitting; on the radial walls there aie 2 4 circular and 

 bordered pits in the field. No undoubted ray-tracheids were 

 noticed ; numerous small pits occur on the horizontal walls of paren- 

 chymatous cells associated with the resin-canals. The pith consists 

 of parenchyma with thin sclerenchymatous diaphragms. 



The horizontal canals, presumably traumatic, in some of the 

 medullary rays resemble in their large size those in Anomaloxylon 

 but in that genus there is no Abietineous pitting on the medullary- 

 ray cells ; similar canals are described by Jeffrey 1 in wounded 

 wood of Cedrus and other Conifers. In the occurrence of vertical 

 canals only in the normal wood Protopiceoxylon is intermediate 

 between Cedroxylon, which has no canals, and Piceoxylon and 

 Pinuxylon of Gothan (= Pityoxylon of Kraus), the fossil represen- 

 tatives of such recent genera as Larix, Picea, and Pinus, in which 

 both vertical and horizontal ducts occur. Gothan holds, and 

 probably with good reason, that vertical canals preceded those 

 in the medullary rays and regards the fossil species as a primitive 

 type. 



A species from the Black Hills described by Knowlton 2 as 

 Pinoxylon dacotense agrees with Protopiceoxylon in having only 

 vertical canals, but it is not clear whether they are normal or 

 traumatic: Piceoxylon would seem to be the more appropriate 

 designation for Knowlton's species. 



Protopiceoxylon articum sp. nov. 



This species is founded on a specimen from Cape Flora, Franz 

 Josef Land, probably Oxfordian in age. Annual rings are distinct 



1 Jeffrey (03); (05). 2 Knowlton in Ward (00) B. p. 420, PI. CLXXIX. 





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