252 Affinities of Fossil Plants from the Palceozoic Rock*. 



affinities with Heterangium, perhaps the most fern-like of the genera 

 grouped under Cycadofilices. The new species is far simpler than any 

 Medullosa hitherto described, for the steles are not only few but are 

 uniform, showing no differentiation into a peripheral and a central 

 system. The small central steles, called " Star-rings " in other Medul- 

 IbsesB, are absent here. In these and other points the species agrees 

 with the genus Colpoxylon of Brongniart, but as that genus is doubt- 

 fully distinct and its leaves are not known, it is not proposed to unite 

 the English species with it. 



In the structure of the petiole and of the leaf generally, Medullosa 

 anglica is as highly organised as any of the Medullosese, and agrees 

 closely with M. Leuckarti, the only other species in which the connec- 

 tion between leaf and stem has been at all satisfactorily proved. 



In the structure of the petioles, and of the roots, in the secondary 

 tissues, and in the secretory canals, which occur throughout the plant, 

 there are clear points of agreement with Cycads, though the primary 

 structure of the stem was that of a Fern. The affinities in the latter 

 direction came out more clearly in Medullosa anglica than in any of the 

 other species as at present known. 



The habit of the leaves, if as appears likely, they were of the Ale- 

 tlwpteris type, must have been fern-like, but that in itself, as the 

 familiar example of Stangeria teaches, is as consistent with Cycadaceous 

 as with Filicinean affinities. 



While Medullosa thus combines, in a striking manner, the characters 

 of Ferns and Cycads, the author is not disposed to regard it as having 

 lain very near the direct line of descent of the latter group. It is more 

 probable, as Count Solms-Laubach has suggested, that the Medullosese 

 represent a divergent branch, which has left no descendants among 

 existing vegetation. 



Medullosa anglica, sp. nov. 



Stem vertical, clothed by large, spirally arranged decurrent leaf- 

 bases, perhaps cast off in old stems. External surface of leaf-bases 

 longitudinally striate. 



Vascular system of stem consisting of a few (usually three) uniform 

 steles, somewhat elongated and lobed as seen in transverse section. 

 Star-rings absent. Interior of each stele wholly occupied by primary 

 wood. 



Secondary wood and bast of moderate thickness, developed on all 

 sides of the steles. Tracheides usually with bordered pits. 



Leaf-traces concentric on leaving the steles, branching and becoming 

 collateral in traversing the cortex. 



Leaf-bases and petioles with the structure of Myeloxylon Landriotii, 

 Ren. 



Leaves highly compound. 



