360 STUDIES IN FOSSIL BOTANY 



outgoing leaf-trace bundles, which are collateral in 

 structure (Figs. 129 and 132). They keep a nearly 

 vertical course for some distance, and do not leave the 

 pericyclic zone until they bend out sharply through 

 the cortex, to enter the bases of the leaves. 



The outer cells of the pericycle have generally 



Fig. 130. — Lygiaodendron oldhamiiim. Transverse section of stem (structure as in Fig. 

 129), surrounded by a mass of foliage, showing rachis and leaflets cut in various 

 directions. On the left, the stem is giving off an adventitious root. X 4. From a 

 photograph by Mr. L. A. Hoodie. S. Coil. 636. 



given rise to a few layers of periderm (Figs. 129, 132, 

 134, pd), which, however, does not reach any great 

 development in Lyginodendron. Beyond the periderm 

 we come to the thin-walled inner cortex, usually ill 

 preserved, and then to the very characteristic outer 

 cortex, consisting of interlacing strands of fibrous 

 sclerenchyma, forming a network, with the meshes 

 occupied by cellular tissue. In transverse section the 



