": 



236 CONIFERALES 



It is suggested by Jeffrey that Araucariopitys may be the stem 

 of Heer's genus Czekanowskia 1 , but there is no proof of a connexion 

 and evidence afforded by Czekanowskia favours an alliance with the 

 Ginkgoales. Araucariopitys is regarded by Jeffrey as ' unquestion- 

 ably Araucarian' though 'nearer in structure to the Abietineae 

 than any other known Araucarian genus living or extinct.' The 

 chief Araucarian feature would appear to be the occurrence of 

 flattened tracheal pits, but Jeffrey points out that not only are 

 the pits in a single row and sometimes separate, but even when 

 in double rows the pits may be opposite. The other characters, 

 e.g., the pitting of the medullary-ray cells and the presence 

 of resin-canals, are more Abietineous than Araucarian 2 . In 

 view of the occasional occurrence in Abietineous genera of con- 

 tiguous and alternate pits on the tracheids it is open to doubt 

 whether there are adequate grounds for assuming a definite 

 Araucarian affinity. Araucariopitys is one of several genera 

 described by Jeffrey and other American authors exhibiting 

 features shared by recent Araucarineae and Abietineae which are 

 claimed as evidence of the greater antiquity of the Abietineous 

 type. In this genus the balance of evidence would seem to be in 

 favour f an Abietineous alliance, the tendency towards an Arau- 

 carian pitting of the tracheids being reminiscent of ancestral 

 types in which that character was more pronounced. 



XI. PROTOCEDROXYLON. Gothan. 



Protocedroxylon araucarioides. Gothan. The type-species of 

 the genus founded on Upper Jurassic wood 3 from the Esmarks 

 Glacier, Spitzbergen, is one of the most striking examples of a 

 group of generalised types from Upper Jurassic strata especially 

 from the Arctic regions. The generic name emphasises the Abie- 

 tineous characters while the specific term gives expression to the 

 presence of Araucarian features. The following account is based 

 chiefly on the description by Gothan, and a few additional facts 

 are taken from an account of some specimens from Liassic and 

 Oolitic rocks on the Yorkshire coast by Prof. Jeffrey 4 and Miss 

 Holden 5 . 



1 See page 63. 2 See also Gothan (10) p. 30. 



3 Gothan (10) p. 27, Pis. v., vi. ^Jeffrey (12) p. 533, PL I. figs, a, b. 



5 Holden (13 2 ) p. 538, PL XL. figs. 1721. 





