XXXIIl] DADOXYLON 253 



refer to circles like annual rings; but Penhallow^ states that 

 there is no evidence of true growth-rings. 



The medullary rays are uniseriate and consist of thin paren- 

 chymatous cells with unpitted walls; they vary considerably 

 in depth, usually comparatively shallow but in some cases 40 or 

 50 cells deep. In recent Araucarineae the rays are generally 

 shallower. The absence of special receptacles, other than 

 occasional resiniferous tracheids, for products of secretion is a 

 feature common to Dadoxylon and the Araucarineae. The phloem 

 presents no features of special interest, but our knowledge of this 

 tissue is comparatively meagre. 



Among other examples of large Dadoayylon stems some of 

 which no doubt bore Cordaitean foliage — though as a rule we 

 have insufficient information as regards anatomical characters 

 to enable a decision to be made between Cordaites and Mesoxylon — 

 reference should be made to the imposing array of silicified trunks 

 in the grounds of the Chemnitz Museum^. These were obtained 

 from Lower Permian strata at Hilbersdorf near Chemnitz from 

 beds overlain by porphyry tuff and resting on quartz porphyry, 

 the volcanic material which furnished the sihceous solutions. 

 Several large pieces of wood were found in association with stems 

 of Medullosa and Psa/ronius, leaves of Cordaites, Artisia pith- 

 casts, and Cardiocarpus seeds with specimens of Walchia, Gompho- 

 strobus and other plants. Sterzel describes a stem 16-5 met. 

 long and 1-5 met. in diameter ; on the main trunk the branch- 

 scars are scattered but on some branches there is a tendency to 

 a whorled arrangement. This and many other stems are referred 

 to Araucarioxylon (or Dadoxylon) saxonicum, a species first de- 

 scribed by Eeichenbach as Megadend/ron saxonicum. In one 

 specimen Sterzel states that the bordered pits are generally in 

 1 — 2 rows, though rarely in 3 — 4 rows, on the radial walls of the 

 tracheids which they do not completely cover: the medullary 

 rays reach a depth of between 20 and 30 cells. It is noteworthy 

 that the stem 1.6-5 met. long has a pith-cast of the Tylodendron 

 type. 



' PenhaUow (00) p. 67. 



2 Sterzel (00); (03); (12). See also Goeppert (80). 



