OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
461 
Fig. 4 represents a section for which I am indebted to Messrs. Cash and Hicks. 
Virtually a vertical one, it has passed obliquely through the outer cortical parenchyma 
at its upper part and traversed the medulla at its lower end. The medullary cells are 
seen at a, corresponding closely with those represented by fig. 3, a, in Plate 19 of my 
Memoir IX.* The vessels of the exogenous zone are traversed almost radially at b, 
and more tangentially at b'. We next have the long, narrow, square-ended cells of 
the innermost bark at c. Above this tissue we obtain double light respecting the 
structure of the spokes of our vegetable wheel seen in the transverse sections. We 
learn that these radiating lines of cells are merely the transverse sections of long, 
vertical, cellular, radiating laminae, cl, which separate large intercellular lacunae, d", 
whilst at d', d' we learn that the constituents of these laminae are very regularly 
disposed cells elongated radially and having a mural arrangement. The cells of the 
outer cortical parenchyma, e, present no special peculiarities. The only additional 
feature noticeable in this section is a small bundle of vessels passing laterally 
outwards at f 
The three sections last described manifestly belong to the same plant in different 
stages of development; but I have now to direct attention to another series of speci¬ 
mens in my cabinet, some of which were first discovered by Mr. Spencer, but to which 
others have been added by Mr. Binns. So far as their cortical structures are con¬ 
cerned they are absolutely identical with those already described. Thus in each of 
the transverse sections, figs. 5 and 6, we have the inner cortical layer at c, the radia¬ 
ting laminae at d enclosing the lacunae at cl", and the outer cortex at e. The differ- 
ences are seen in the structure of the vasculo-medullary axis—and especially of its 
central portion. This appears in both the sections figured to be largely if not 
entirely vascular, and others in my cabinet exhibit the same characteristic aspect. 
The exogenous vascular zone, b, also exhibits much less definitely the grouping of the 
radiating vascular laminae into distinct wmclges than is the case with the section, fig. 3. 
At the same time we fail to discover that grouping even in fig. 2, though the sec¬ 
tion there represented possesses the large cellular medulla so characteristic of fig. 3. 
In fig. 6 we find the lacunae and radiating cellular laminae replaced at cl’" by a mass of 
coarse cellular parenchyma, and from which a vascular bundle is seen emerging at f 
Fig. 7 is an instructive section for which I am indebted to Mr. Spencer. It 
appears to combine features seen in figs. 5 and 6 with others seen in fig. 1, and is 
further valuable since it illustrates the strong tendency to develop branches which 
seems to characterise this plant. 
At the upper extremity, A, of the figure we have a nearly transverse section of an 
axis which has corresponded closely with fig. 1. At a we have an axial cluster of 
vessels, not arranged in any regular order, or surrounded by an exogenous zone. At 
c are the narrow elongated cells of the innermost cortex, intersected obliquely, whilst 
* I may add that I have a true vertical section of another specimen of the new plant which is almost 
a facsimile of the main axis of fig. 2 in Plate 19 of my ninth memoir already referred to. 
mdccclxxxiii. 3 o 
