Mandiester Memoirs, Vol. xlvi. (1902), No. 0, 5 



with a dense black mass, rendering portions of the tissue 

 quite opaque. Where the cells are visible, they are small 

 and arranged sometimes in fairly regular radial rows, 

 sometimes in groups, not unlike those I have described 

 for the phloem of LepidopJiloios and Lepidodendi'on. 



A lacunar zone is not developed, though in one or two 

 places lacuna; appear in process of formation in the 

 phloem region, and, as I have pointed out elsewhere,* 

 the lacunar tissue probably represents only a defectively 

 preserved phloem region. 



The phloem is, like the xylem, definitely interrupted 

 by broad primary medullary rays consisting of par- 

 enchymatous cells exhibiting some radial elongation. 



No definite pericycle can be distinguished, though it 

 is possible that one or more of the layers of cells 

 designated as the inner cortex may have partaken of the 

 nature of a pericycle. 

 3 The cortical tissues. 



The cortical tissues are much better preserved in 

 XeiiopJiyton than is usually the case in Stigmaria, and it 

 is to the almost perfect preservation of its middle cortex 

 that a transverse section of Xenophyton owes its charac- 

 teristic appearance. As in the stem of the LcpidodendrecB, 

 one can distinguish in Xenopliyton an inner cortex (the 

 "problematical pericycle" of Hick), the middle cortex 

 ("radicular tissues" of Hick), and the outer cortex ('' true 

 cortex '' of Hick). 



The inner cortex forms a sheath of more or less 

 closely-set cells, five or six layers in thickness, around the 

 stele. The cells seen in transverse section {Plate XI., 

 Fig. 2) are smaller in diameter than the cells of the 

 middle cortex. They are elongated in the direction of 

 the long axis of the Stigmaria, and fitted together by 

 * Weiss, F. E. ('oi). 



