162 



STUDIES IN FOSSIL BOTANY 



parts, which for some distance have the form of horse- 

 shoes, with the pith of each stele open towards the other. 

 Where there was secondary growth, the cambium in this 



Fig. 66. — Lepidodendron selaginoides. Transverse section showing the two steles 

 (A and B) of a bifurcating stem, a, pith ; b 1 inner cortex ; c, leaf-traces ; h, secondary 

 wood. The pith in this species only exists near a bifurcation, where the steles are 

 still incomplete on the inner side. X about 9. After Williamson, Phil. Trans. 

 Will. Coll. 340. 



region sometimes extended into the medulla, forming 

 an inverted band of secondary tissues within the primary 

 wood. This occurred even in L. selaginoides, where the 



