714 MR W. T. GORDON ON 



growing from the centres of crystallisation have so distorted the cells that the latter 

 have become completely disintegrated. When the small spherules had grown out so 

 as to touch each other, the carbonaceous matter from the ruptured cortical tissue was 

 imprisoned between them, and thus a pseudo-cellular structure was produced. Each 

 individual spherule resembles a cell, but careful examination shows that the outlines are 

 not really cell walls. This has occurred throughout the whole block, so that, at first 

 sight, the entire mass appears to be a continuous cellular tissue with various xylem - 

 strands traversing it. Closer examination, however, reveals the true nature of the 

 pseudo-cellular structure, and shows that the various strands really belong to separate 

 and distinct plant fragments. Plate I. fig. 11, illustrates this structure exceedingly well. 

 At first sight, the strands St., pet. tr., rt. tr., z and z' are all apparently set in a continu- 

 ous parenchymatous tissue, but a comparison with PL I. fig. 10 shows that the strands 

 st., pet. tr., and rt. tr., belong to one plant, while z and z' are really outside the 

 cortex, though the pseudo-cellular nature of the whole matrix masks this to a large 

 extent. 



Although the peculiar preservation obliterates the softer tissues, there is no difficulty 

 in delimiting their extent, and so continuity can be established between the stems and 

 the other members. This continuity is confirmed by a study of the xylem tissue, which 

 is continuous in all cases. Indeed, it is largely from a consideration of the xylem that 

 the results to be described below were obtained. 



In a Preliminary Note read to the British Association at Winnipeg,* I gave this plant 

 the provisional name — Zygopteris petty curensis, but indicated that I expected to be 

 able to demonstrate that it really was identical with Zygopteris romeri (Solms), and this 

 has proved to be the case. Before considering the general structure, however, it will be 

 well to recall the history of this interesting species. Like many another fossil, this plant 

 has had a checquered history. In 1892 Count Solms-Laubach (11) gave the name 

 Zygopteris romeri to detached petioles with peculiar traces. These specimens were 

 obtained by Solms and Herr Volgel from the Devonian of Falkenberg. Similar 

 petioles were discovered in the Lower Carboniferous rocks of Esnost in France and called 

 Diplolabis esnostensis by Renault (8) in 1896. In 1908, M. Pelourde (7) described a 

 partially disintegrated specimen from Esnost under Flicheia esnostensis. This new 

 genus and species is identical with some of my specimens which can be traced into the 

 normal petiole-strand of Diplolabis romeri. The five strands are derived by the arms of 

 the trace breaking away from the horizontal bar. An example of a rotted trace com- 

 parable with those figured by this author is reproduced in PI. IV. fig. 46. M. Paul 

 Bertrand (2), in 1909, recognised that Renault's specimens were identical with those 

 of Solms, and has therefore reverted to the original specific name romeri, while retain- 

 ing Renault's genus Diplolabis. This course I have also followed here. 



The specimens from Pettycur are much more complete than those previously 

 obtained elsewhere, and my work on them has convinced me that we are dealing with a 



* Report Brit. Assn., Winnipeg, Section K, 1909. 



