of Coal-Measure Plants. 285 



side. That this secondary wood belongs to the trace is shown by 

 the length of the row of woody elements, the small tracheides 

 towards the periphery, and the signs of rupture at the base of 

 the trace. 



In this section an adventitious root is also seen passing 

 through the cortex. 



Slide 181. 



A radial longitudinal section, showing the structure of the 

 medulla and the wood. In the medulla, the sclerotic nests are 

 seen to be several cells thick. The section also passes through 

 a primary bundle. The medullary rays are muriform, and of 

 considerable height. The tracheides of the secondary wood show 

 the usual multiseriate reticulation of bordered pits on the radial 

 walls. Binney 1 speaks of these, as being " divided by oblique and 

 transverse dissepiments placed at great distances." These divi- 

 sions are apparently due to cracks, or other imperfections of the 

 preservation, and I have not observed in the specimen any certain 

 indication of definite transverse walls. The section is bounded at 

 one end by a portion of ill-preserved periderm, and at the other 

 by a series of sclerotic nests in the pericycle. 



Slide 182. 



The tangential longitudinal section passes through the se- 

 condary wood, and a parenchymatous band of the outer cortex. 

 The tracheides are somewhat flexuous, and bear here and there 

 reticulate pittings. Numerous transverse partitions are seen, as 

 in the radial section, but these again are due to imperfect preser- 

 vation. The medullary rays consist of 1 — 4 rows of small rounded 

 cells. Occasionally a chain of much larger, oval, or rounded 

 cavities, is found occupying the position of the ray, and often 

 surrounded by the ordinary ray cells. These " much larger 

 cellules," which Binney notices, are no doubt due to the disruption 

 of more than one series of the cells of the ray. 



In the pericycle, the section has passed through a series of 

 sclerotic nests. The inner cortex, and the parenchymatous zone 

 of the outer cortex, through which the section passes, are very 

 badly preserved, only occasional fragments of the cells being seen. 



1 Binney, in Williamson, Phil. Trans. 1873, p. 377. 



