I20 Dr. W. C. Williamson 07i 



Transverse. 

 Medulla. 



Q. — p. 200, Figs. 23, 24, and 25, C.N. 420 to 425. 



Primary Tracheal Cylinder. 



Q. — p. 200, Figs. 23, 24, C.N. 420-421. 



Q. — p. 200, Fig. 25. C.N. 422 to 426. 



Q.— p. 200, Fig. 23-24-25, C.N. 420, 421, 424. 



Special Cells in the circular loops. 



O. — p. 200, Figs. 25e' and 27, C.N. 425. 



Tjpe of Lepidodendron niacropJiyllinn. Will. 



A very rare form, of which not more than two specimens 

 (possibly only one) has been discovered. The plant was 

 described by Mr. Carruthers in January, 1872, at a meeting 

 of the Royal Microscopic Society, and I figured it in a 

 Memoir presented to the Royal Society in February of the 

 the same year (C. Fig. 35). In its general features it 

 approximates to the type of L. Harcourtii, but is dis- 

 tinguished by the structure of its leaf-traces, by its more 

 robust character, and most of all by the large size of its 

 leaf-sections. Mr. Carruthers described it as having no 

 medulla — but this is a mistake. He also thought that its 

 leaf-trace divided into two. But at that date we were all 

 alike ignorant of the true structure of Lepidodendroid 

 leaves. The apparently divided leaf-trace is really the 

 leaf-trace, plus one of the lobes of the double paricJinos. 

 There is also an adenoid organ present.* Though this is 

 obviously a distinct form of Lepidodendron^ additional 

 examples, affording further information respecting it, are 

 much to be desired. Like the rest of its tissues its leaf- 

 traces are remarkable for their robustness. 



Medullary Cavity. 



C- . 298, Fig. 35, C.N. 377. 



• For these terms see the Memoir XIX, i.e. B.B. 



