CORDAITEAE 529 



been used to distinguish the wood of Cordaites from 

 that of other families, such as Poroxyleae and Calamo- 

 pityeae, but the distinction does not always hold good. 



We see, then, that, so far as' the secondary wood is 

 concerned, the structure of Cordaites is indistinguishable 

 from that of a Conifer, of the family Araucarieae. 



The phloem, when preserved, shows a radial arrange- 

 ment of its elements, corresponding to that in the wood 

 (see Fig. 189,^). Sieve-tubes and phloem-parenchyma 

 have been distinguished, and in some forms bast-fibres 

 are also present. 



The parenchyma of the primary cortex was traversed 

 by secretory sacs, and strengthened by many radial 

 bands of fibres, which formed a hypodermal system, 

 and also extended deeply into the inner cortical tissues 

 (Fig. 189, c). These fibrous strands have a vertical 

 course, and are rarely found to anastomose. 



The bundles passing through the cortex on their 

 way to the leaves are often met with in transverse 

 sections of the stem (Fig. 189, l.f). In the neighbour- 

 hood of the out-going leaf-trace, in the species figured, 

 the cortex is parenchymatous, the fibrous strands being 

 absent (see Fig. 189). The leaf-trace was very often 

 a double one, a point to which Williamson called 

 attention long ago, as offering a close analogy with 

 Ginkgo among recent Gymnosperms. 1 It will be 

 remembered that we have found a double leaf-trace in 

 Lyginodendron, Ptychoxylon, Poroxylon, and other cases. 



1 Williamson, " Organisation of Fossil Plants of Coal-measures, " Part xii. 

 p. 470, Phil. Trans. 18S3, Part ii. In the section here figured (Fig. 189) 

 each bundle of the double trace is subdivided. This represents a. natural 

 fission ; in some forms of Cordaites it has been observed that a number of 

 bundles entered the base of the leaf. 



