CORDAITEAE 



527 



The secondary wood has essentially the structure of 

 that of Araucaria, and was hence named Araucarioxylon 

 by Kraus, 1 a name which is now superfluous in cases 

 where the connection with Cordaites has been estab- 

 lished. The bordered pits, which are limited to the 

 radial walls, are usually in two or more rows, and are 



-Srf2d 



If 



■fc8?C*A 



m 



Fig. 189. — Cordaites, sp. Part of transverse section of a stem, from the English Coal- 

 measures, p, pith ; x, zone of wood ; ph, phloem ; //, double leaf-trace, each bundle 

 subdividing ; c, cortex, containing sclerenchymatous strands. X about 6. S. Coll. 

 306. (G. T. G.) 



densely crowded in alternating series, the borders thus 

 having a hexagonal outline (Fig. 190, B, bt). In good 

 material, the pore of the pit can be recognised clearly, 

 and has the form of an inclined elliptical slit. Certain 

 variations in the diameter of the tracheides of successive 

 zones were regarded by Renault as indicating periods 



1 The names Dadoxylon, of Endlicher, and Araucarites, of Goppert, 

 are often used in the same sense as Araucarioxylon. Dadoxylon is prefer- 

 able in so far as it does not suggest any affinity with the Araucarieae. 



