REMAINS OF STEMS OF DOUBTFUL AFFINITY, ETC. 



359 



of wood, and like them are separated from one another by broad medullary 

 rays. The middle layer is the parenchymatous inner rind which is seldom 

 preserved ; its closed tissue contains many isolated darker cells. Lastly, the 

 outer rind is always well preserved ; it consists of thick-walled elements, 

 and is traversed by hypodermal fibre-plates which appear on the transverse 

 section as crowded radial stripes. The tangential section shows that these 

 plates have a sinuous course, so that they meet in places and coalesce with 

 one another for short distances. In this way fusiform meshes filled with 



FIG. 49. Lyginodendron Oldhamiamum, Will. Transverse section of the stem according to a preparation from 

 Oldham in my possession ; in the centre the parenchyma of the pith partially preserved, and on its outer boundary six 

 irregularly distributed primary bundles with centripetal formation. Next to this on the outside is the ring of wood, 

 which is very like that of Cycadeae. Outside the wood, where the bast-portion has disappeared, are seen in several 



laces the transverse sections of bundles lying side by side in pairs, which probably belong to the emerging leaf-traces, 

 ingle similar strands (a) showing growth in thickness perhaps, answer to their lowest portion. Inner and middle rind 

 are destroyed ; the outer rind shows Dictyoxylon-structure. 



parenchyma are formed between them ; we have in a word the well-known 

 Dictyoxylon-structure (Fig. i). 



Further investigation is required to make us fully acquainted with the 

 structure of the bundles which pass from this ring of wood to the lateral 

 members. At present there is scarcely anything satisfactory to tell about 

 it. Bundles of different character are met with in the inner rind on every 

 transverse section, but it has not hitherto been possible to determine their 

 course with certainty in the longitudinal direction. These bundles occur in 

 three principal forms. The most frequent are bundles of somewhat irregular 

 roundish-ovate form on the transverse section, which lie side by side in 



