Yol. 59.] OCCUKKENCE OF DICTYOZAMITES IN ENGLAND. 223 



reason for the use of different names for plants, which are either 

 specifically identical or very closely allied, is to be found in the 

 individual preferences of authors in the choice of possible generic 

 designations for a particular plant. 



In order to obtain a clear idea of the botanical relationship of 

 one flora to another it is essential to devise some method by which 

 distinctions, either imaginary or exaggerated, between plants re- 

 corded by different writers under distinct names may be eliminated. 

 As a standard of comparison we may take a list of the plants 

 described from the Inferior -Oolite rocks of Yorkshire, and by 

 adopting an uniform system of nomenclature, and regarding as 

 representative species types that are either specifically identical or 

 distinguished by characters that, so far as we can judge, are not of 

 generic rank, we shall be in a better position to furnish an answer 

 to the question — how closely do the widely separated floras of 

 Japan and "Western Europe resemble or differ from one another ? 



In the following lists (pp. 224-26) I have therefore made use of 

 specific names in a wide sense. In taking considerable liberties 

 with the nomenclature of other authors, I do not necessarily mean 

 to express disagreement with them as regards their interpretation 

 of affinity, but my aim is to avoid the danger of allowing slight 

 differences — whether of specific rank or not — to obscure the broad 

 relationships of floras. The method of comparison is adopted 

 primarily for the purpose of instituting a botanical comparison, 

 rather than with the view of expressing an opinion as to relative 

 age or stratigraphical position. The data on which the lists are 

 founded have been supplied by the works of Geyler, 1 Yokoyama, 2 

 and Nathorst 3 in the case of the flora of Japan, but the flora with 

 with which we are more especially concerned is that described by 

 Dr. Yokoyama in his earlier paper of 1886 ; by Oldham & Morris 4 

 and by Feistmantel 3 for the Indian species; and by Bartholin, 6 

 Moller, 7 and Hjorth * for Bornholm. 



The welcome memoir by Dr. Moller on the flora of Bornholm 

 deals only with the Pteridophyta, but we may look forward to a 

 completion of his valuable investigations at an early date. [Since 

 this paper on Dictyozamites was read, Dr. Moller's second memoir 

 on the Bornholm Flora has been published ; see Moller (03) in the 

 Bibliography, p. 231.] 



In order to avoid misunderstanding, the names employed by the 

 authors of the floras of Japan, India, and Bornholm are added in 

 square brackets in cases where their nomenclature or determination 

 does not agree with that which I have adopted. The initial letters 

 Y, F, BT, B. and M (Yokoyama, Feistmantel, Nathorst, Bartholin, 

 and Moller), placed after the specific names in the last three 

 columns, serve as a guide to the ' Floras ' from which the species 

 are quoted. 



1 Gevler (77). 2 Yokoyama (90) & (95). 



3 Nathorst (90). 4 Oldham & Morris (63). 



5 Feistmantel (77) & (77 2 ). 6 Bartholin (92) & (94). 



7 Moller (02). * Hjorth (99). 



