202 



CLADOXYLEAE 



[CH. 



occasional smaller oval or cylindrical stele embedded in a ground- 

 tissue composed of thick-walled cells. The plates are curved 

 like a U or sinuous and not infrequently anastomosing. In a 

 section of this type figured by Unger the vascular plates appear 

 to form a complex anastomosing system, but Solms 1 states that 

 the drawing exaggerates the amount of fusion between the strands, 



G 



FIG. 459. A, Cladoxylon mirabile, section of stem; B, Cladoxylon taeniatum, 

 section of stem ; C, Cladoxylon dubium, section of stele ; D, C. dubium, section 

 of stem; E, Cladoxylon (?) mirabile, section of petiole; F, Syncardia pusilla; 

 G, development of leaf -trace in Cladoxylon taeniatum. (A E, after Solms- 

 Laubach; F, after Unger; G. after P. Bertrand.) 



and an examination of a section in the collection of the English 

 Geological Survey cut from Unger's specimen enables me to 

 confirm this statement. Each vascular plate consists of a narrow 

 median region composed of primary tracheids with a scalariform 

 type of pitting surrounded by secondary tracheids with inter- 

 spersed medullary rays one cell broad. The thickness of the 



1 Solms (96) B. p. 53. 



