TRANSACTIONS OF SECTION C. 629 



several of my sections this peculiar structure is well shown. It consists of a large- 

 celled paienclivma of very loose texture, and may be divided into an inner and 

 outer hark. The inner portion is formed of three or more rows of hrick-like cells 

 surrounding- the woody zone, while the outer epiderm is formed of one or two rows 

 of very large cells having a thick outer wall, the whole structure being little 

 better than an epidermal layer, and of a very perishable nature. The roots of these 

 beautiful plants have not yet been described, but I have good reasons for believing 

 that the specimens I am now about to describe belong to them. 



Professor Williamson has described two very singular plants from the Lanc.i- 

 shire coal-field, under the generic name of Amyelon. One of these he has shown 

 to be the root of Asterophyllites. This root appears to be rare in our Yorkshire 

 coal-strata, but the other, A. radicans, is not unfrequently met with, I have lately 

 found one or two new forms of these pithless roots, which appear to be closelj'' 

 allied to the latter species. One of these has a solid vascular cylinder consisting 

 of radiating laminae, the outer vessels of which are the largest, the vessels 

 gradually becoming smaller as they approach the centre. Laminse of small vessels 

 and medullary rays intermingle at the circumference with laminse of large ones ; 

 but as they converge towards the centre many of them coalesce with one another, 

 so that even there the vessels do not become so small as they otherwise would do, 

 and thus preserve an open network arrangement which gives the plant a very 

 striking appearance. The bark, of which only a small portion is preserved, is 

 almost identical in structure with that of Astromyelon. 



The other root has a much smaller central axis, but it presents a striking 

 diiference, in the fact that its large-celled thick bark is nearly always present, 

 I have many specimens of this root, and the majority have the bark fairly pre- 

 served. The structure of its vascular cylinder more nearly resembles that of 

 Amyelon radicans than that of the other does; but the vessels are, as a rule, 

 much smaller, and they are barred in the radial sections, wliile those of 

 A. radicans are i-eticulated. AVhile writing, both these plants are before me, and 

 the difference in their vascular cylinders is most striking, especially in respect to 

 the markings on the vessels, and also in respect to the beautiful state of preserva- 

 tion of the bark in my plant and its absence in the other. The bark is about as 

 thick as half the diameter of the woody cylinder, and is composed of an inner layer 

 of delicate mural parenchyma, and an outer epiderm of large cells, but of very 

 irregular size, the middle portion being a combination of the two forms. Some- 

 times the structure is composed of large cells of more uniform size. 



The next problem to solve is, to what plants do these roots belong ? As the 

 result of a very careful examination of a large series of specimens, I have come to 

 the conclusion that they are the roots of Astromyelon. It would extend this 

 abstract too far to go into the subject fully, but I may mention two or three 

 of my reasons for coming to this conclusion. In the first place, the large open cells 

 and vessels of these plants are exactly what one would expect to find in the root 

 of Astromyelon, just as we find the vessels of the vascular cylinder of Stigmaria 

 agreeing with those of the ligneous zone, in the Lepidodendra. The very younc 

 forms of Astromyelon largely partake of the character of these roots. In longi- 

 tudinal sections the vessels in both plants are identical. In the radial sections of 

 both, the vessels are seen to be barred. The structure of the bark is also identical 

 in both stem and root, and lastly I have invariably found the two associated in the 

 same material. Being uncertain whether these two roots are merely diff'erent 

 forms of one species, I propose to unite them provisionally under the name of 

 Amyelon radiaius. 



8. On the Palceozoic Rocks of North Devon and West Somerset. By 

 W. A. E. USSHER, F.G.S., Oeological Survey of England and Wales. 



The author gave a brief introductory outline of the different opinions which 

 had formerly been entertained respecting the structure of North Devon and West 



