;i6 



STUDIES IN FOSSIL BOTANY 



Branching and anastomosis of the strands are found at 

 many places. 



In the great majority of the xylem-strands the 

 structure is definitely mesarch, the spiral protoxylem- 

 elements lying in the interior (Fig. 186, px). The 



Fin. i36. — Pitys antiqua. From a transverse section of the stem. f./>, primary xylem- 

 strand embedded in the pith ; fix, protoxylem ; .r 2 , inner part of secondary wood ; 

 m.r, medullary rays. The cells with black contents may be secretory sacs. X 73. 

 Kidston Coll. 59SA. (G. T. G.) 



primary tracheides are accompanied by a little xylem- 

 parenchyma. 



No spiral elements could be detected at the inner 

 edge of the woody zone, so it would appear that the 

 primary wood is represented only by the medullary 

 strands. The considerable separation between the latter 



