285 
of Coal-Measure Plants. 
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. 
