502 STUDIES IN FOSSIL BOTANY 



was traversed by numerous parallel veins. 1 This is 

 quite a different type of leaf from anything we have 

 met with among the groups already considered. 



The structure of the stem, however, is of a type 

 already familiar to us. The transverse section of a 

 young stem is represented in Fig. 1 8 1 , B. We see at 

 once that there is a well-marked pith, surrounded by 

 a ring of collateral vascular bundles. The primary 

 xylem-strands of these bundles, which border immedi- 

 ately on the pith, are clearly marked off from the 

 surrounding zone of radially arranged secondary wood, 

 which is succeeded externally by the well-preserved 

 cambium and phloem. The stem thus had secondary 

 growth in thickness, of a normal character. The 

 pericycle, immediately surrounding the phloem, and 

 the inner primary cortex, contain structures interpreted 

 as gum-canals, and similar organs are also present in 

 the pith. The outer cortex was strengthened by a 

 system of hypodermal strands of sclerenchyma, such as 

 we have so often met with in the stems of Palaeozoic 

 plants. The general anatomy of the stem is thus 

 strikingly similar to that of a Lyginodendron, and a 

 more detailed examination shows that the resemblance 

 is a real one. A general agreement with Calamopitys 

 is also evident. 



The bundles surrounding the pith are rather more 

 numerous than in Lyginodendron, a fact which is 

 correlated with the more complex phyllotaxis of 



1 The leaves, or at least their laminae, do not appear to have been 

 found in connection with the stem, in these species, but as MM. Bertrand 

 and Renault pointed out, the close anatomical agreement between stem 

 and leaf established a strong presumption that the two organs belonged 

 to identical or closely related species. In the British species, P. Sutcliffii, 

 the connection between the stem and leaf-bases is clear. 



