XLIV] DADOXYLON 177 



wood has already been criticised l : it is pointed out that the appli- 

 cation of an age-test is scientifically unsound and cannot fail to 

 be misleading. Although it is probably true that species of 

 Dadoxylon from strata later than the Rhaetic series are in the 

 majority of cases Araucarian, we have no adequate grounds for 

 definitely naming such types Araucarioxylon in the sense of 

 membership of the Araucarineae. Similarly some Palaeozoic 

 species of Dadoxylon may well be more closely allied to the Arauca- 

 rineae than to Cordaites: Dadoxylon valdajolense (Moug.) 2 and 

 D. Rhodeanum (Goepp.) 3 have both been referred to Walchia: the 

 latter species is included by Tuzson in the genus Ullmannites. We 

 do not know the lower geological limit of the Araucarineae, nor 

 do we know when the Cordaitales became extinct. Tuzson 4 

 subdivides wood of the Dadoxylon type into several genera in- 

 cluding Pycnophyllum, to which is referred Dadoxylon Brandlingii 

 (Lind. and Hutt.), Ullmannites applied to the type recently 

 named Eristophyton Beinertianum by Zalessky and previously in- 

 cluded by Scott in Calamopitys, also to Dadoxylon Rhodecumm 

 and D. saxonicum, Pagiophyllites, including P. keuperianus 

 (Goepp.), and for Tertiary species the term Araucarites is used. 

 This nomenclature, based partly on age and in part on a supposed 

 connexion between the wood and foliage-shoots, is opposed to 

 sound principles and in some cases is at variance with the true 

 character of the species. When evidence is available in support of 

 a reference either to the Araucarineae or to the Cordaitales the 

 qualifying terms Cordaioxylon or Araucarioxylon may be added 

 after Dadoxylon. Such a species as Dadoxylon permicum Merck. 5 

 is one of many examples of a Dadoxylon that cannot be more pre- 

 cisely identified. Dadoxylon australe Crie 6 from Triassic rocks in 

 New Caledonia must be included in the same category. This 

 species is founded on wood showing well-marked rings of growth ; 

 there are two or more rows of alternate polygonal pits on the radial 

 walls of the tracheids and the medullary rays are uniseriate and 

 3 15 cells in depth. Crie's species should not be confused with 



1 See p. 249, Vol. m. See also Gothan (05) p. 14; Potonie (02) p. 229. 



2 Fliche(03); Mougeot (52) A. 



3 Potonie (99) B. p. 294; Gothan (07) p. 17; Tuzson (09) p. 34. 



4 Tuzson (09) p. 17. 5 Mercklin (55) p. 53. 

 6 Crie (89) p. 5, Pis. j., in., v. 



s. iv 12 



