1877.] 



Fossil Plants of the Coal-measures, 



415 



dendroid features. The provisional name of Rachiopteris cylindrica is as- 

 signed to it. 



Two fragments have been met with that correspond very closely with 

 some figured by M. Grand'Eury as belonging to Cordaites. One of these 

 is a fragment of epidermis densely crowded with stomata ; the other is 

 part of the transverse section of a leaf exhibiting a single row of vascular 

 bundles. 



The Arran beds have furnished a very striking fragment of wood to 

 which fee lecturer gives the name ot^Lyginodendron anomalum, and which 

 appears to exhibit, in a most exaggerated form, the peculiarities of the 

 vascular axis of t^io^Lyginodendron Oldhamium previously described. Its 

 remarkable characteristic is the enormous size of its medullary rays, which, 

 in tangential sections of the wood, have a lenticular shape — a contour 

 which causes the thin vascular laminae, when seen in such sections, to 

 form a perfect network, the large meshes of which are occupied by the 

 cells of the medullary rays. 



The Oldham nodules frequently furnish fragments of the bark of some 

 large trees. One of the most perfect of these is described, and consists 

 of an inner parenchyma, radiating into a very thick layer of prismatic 

 parenchyma, and an outer one of the more common type of parenchyma. 

 Intermediate between these two latter is a very remarkable zone of meri- 

 stem tissue where active genetic action has obviously gone on during the 

 life of the plant. There thus appear to have been two parallel cylindrical 

 zones of active growth in this bark — one between the vascular cylinder 

 and the innermost bark, and the other between the prismatic tissue or 

 modified bast layer and the subepidermal parenchyma. At the junction of 

 the two latter tissues the tangential sections show that the prismatic cells 

 are grouped in undulating vertical laminse, forming a network, the meshes 

 of which are occupied by tabular parenchymatous cells which stand on their 

 edges with their flat planes arranged tangentially to the stem. These 

 cells indicate an extremely active state of cell-multiplication. There is 

 every probability that this type of bark is Sigillarian. 



Some curious little circular disks, surrounded by a ring of seven or 

 eight yet smaller disks, are described : they are from Halifax. Their 

 nature being problematical, the provisional name o^^Oidospora anomala is 

 assigned to them. The lecturer concludes by calling attention to the 

 remarkable prevalence of prismatic parenchymatous cells in Calamites, 

 Lepidodendron, Sigillaria, and Aster ophyllites, in the medullary rays of 

 Calamites, and especially in the middle bark of all these plants, where it 

 has constituted a modified form of phellem or corky tissue. 



