14 WATSON, Two Species of Lepidodendron Harcourtii. 



a small portion of the xylem ring separating off and 

 passing out, carrying with it a corresponding piece of 

 phloem. (Figs. I — 2, Plate I.) 



In most cases the continuity of the xylem ring of the 

 main stem is not broken, only some of the more external 

 tracheids going to form the branch bundle. 



An interesting point is that the parenchyma occupy- 

 ing the gap thus left in the main axis often contains short 

 tracheids, the barred cells of Williamson. 



The branch bundle is from the first surrounded by its 

 own series of leaf traces. 



When the branch bundle reaches the outer cortex it 

 is radially symmetrical and does not contain a pith. 



After the branch has become free it gains a pith of 

 very small dimensions and has all the structure of a larger 

 branch. 



These Halonial branches usually retain a compara- 

 tively well preserved middle cortex of the ordinary type. 

 They are covered with leaf bases of large size, and present 

 no special characters. 



Application of the term Halonial to these branches. 



The generic term Halonia was founded by Lindley 

 and Hutton in 1833. Their description of the generic 

 characteristics is somewhat indefinite, but they state that 

 the tubercles are "at intervals of ^ in. every way," thus 

 suggesting that the quincuncial arrangement of the 

 tubercles is an essential character of Halonia. 



Since this time many authors have referred to 

 Halonia, and established the fact that it is the fruit-bearing 

 branch of a Lepidodendroid tree. Further, in all cases 

 where the leaf scars are well preserved, they belong to 

 Lepidophloios. (Kidston, '93, very full account of litera- 

 ture.) 



