250 Dr. D. H. Scott. On the Structure and 



any others at present known, and lastly, the greater simplicity of their 

 structure causes the essential characters of the genus to stand out with 

 greater clearness than in the more complex species. The specimens 

 were discovered by Mr. G. Wild and Mr. J. Lomax, in material from 

 the Hough Hill Colliery, Staly bridge. The sections have been cut, 

 with the greatest skill and success, by Mr. Lomax, and are very 

 numerous, about 100 sections, transverse and longitudinal, having 

 been examined from one specimen alone. 



The principal specimens are four in number, in addition to which 

 other fragments have been included in the investigation. The species, 

 which is very distinct from any form previously described, will be 

 known as Medullosa anglica ; a diagnosis is given below. 



The most complete specimen of the stem has a mean diameter of 

 rather more than 7 cm., including the adherent leaf -bases. The 

 others do not appear to have been very different in dimensions. 



The large leaf-bases, to judge from the most perfect specimens, 

 almost completely clothed the surface of the stem. They were de- 

 current, and confluent with the stem for a vertical distance of 13 cm. 

 or more, the diameter of the petiole, where it became free from the 

 stem, being about 3 or 4 cm. The arrangement of the leaves was a 

 spiral one, and in the only case where the phyllotaxis could be deter- 

 mined, the divergence proved to be 2/5. 



In two of the specimens the external characters of the fossil are 

 well shown. The outer surface of the long leaf-bases is marked by 

 a conspicuous longitudinal striation, the ribs (which would not have 

 been so prominent during life) representing the fibrous strands of the 

 hypodermal tissue. The habit of the stem, clothed with the long, 

 almost vertical, overlapping leaf-bases, may have been not unlike that 

 of some of the tree-ferns, such as Alsopliila procera. 



The vascular system of the stem consists of three (or locally four) 

 steles, anastomosing and dividing at long intervals. Each stele has an 

 elongated, somewhat irregular, sectional form, and is composed of a 

 central mass of primary wood, surrounded by a zone of secondary wood 

 and phloem. The primary wood, which is very well preserved, is made 

 up of tracheides and conjunctive parenchyma, with the spiral elements 

 (protoxylem) scattered near its outer margin. The secondary wood 

 consists of radial series of tracheides and medullary rays ; the secondary 

 tracheides bear multiseriate bordered pits on their radial walls ; most 

 of the primary tracheides are pitted in the same way, but on all sides 

 alike. In the neighbourhood of the protoxylem-groups the tracheides 

 of the primary wood are spiral or scalariform. The phloem is made 

 up of elongated elements, presumably the sieve-tubes, forming a net- 

 work, the meshes of which are occupied by the phloem-rays. 



Each stele of Medullosa anglica shows the closest agreement in struc- 

 ture with the single stele of a Heterangium, so that the stem of this 



