256 CORDAITEAE [CH, 



in Natal and Zululand have been described by Warren 1 as Dado- 

 xylon austmle Arb., showing interesting anatomical features, but 

 the material almost certainly includes more than one specific 

 type and would repay more detailed investigation. 



Dadoxylon materiarum Dawson. 



This species was described by Dawson 2 from Carboniferous 

 strata in Nova Scotia and afterwards referred by Penhallow 3 to 

 the genus Cordaites. In the transverse section reproduced in 

 fig. 474, A, the tracheid-walls have been reduced in thickness 

 by partial decay, but some of the bordered pits are clearly shown 

 on the radial walls ; the pits usually form 2 4 contiguous rows 

 (fig. 475) in some cases with an oblique pore while others are 

 represented either by the outer border of the pit or by the pore 

 only. The narrow medullary rays are as a rule uniseriate and 

 may be 60 cells deep (fig. 474, ' B). Dawson states that some 

 specimens have large Artisia pith-casts, a fact that formerly 

 would have been regarded as proof of the Cordaites nature of the 

 wood, but in the absence of evidence with regard to the nature 

 of the primary xylem it is impossible to say whether the stem 

 is Cordaites or Mesoxylon. 



Dadoxylon sp. 



Some wood received from Mr Leslie, collected at Vereeniging,. 

 South Africa, in Permo-Carboniferous rocks, shows well-defined 

 rings of growth. The pits form either a single row, a double^ 

 alternate and contiguous row, or rarely three series on the tracheid 

 walls. The medullary rays are usually uniseriate and 1 30 cells 

 deep. 



Dadoxylon Kayi Arber. 



This species is represented by some large trunks, in some 

 cases with a diameter of 40 cm., discovered by Mr Kay in the Coal 

 Measures of Worcestershire 4 . The pith is very small and shows no 

 indication of a discoid structure, but owing to its poor preserva- 

 tion no sections could be obtained of this region. The secondary 

 wood is characterised by the large number of uniseriate medullary 



1 Warren (12). 2 D awson (63 2 ). 



3 Penhallow (00) figs. 13, 14, 17. 4 Arber, E. A. N. (13 2 ).- 



