138 THE GEOLOGICAL HISTOBY OF STBATIOTES. [vol. lxxix, 



Discussion". 



Mrs. E. M. Reid stated that this was the first attempt to trace 

 the geological history of a genus of plants through a study of 

 fossil fruits and seeds. Owing to the comparative novelty of the 

 subject and the few deposits examined in this way, the knowledge 

 of the geological range of species was usually very imperfect,, 

 though a considerable amount was known of the fossil history of 

 many genera on the botanical side. In the case of Stratiotes the 

 abundance and marked character of the seeds early attracted the 

 attention of geologists, and much material was collected. With 

 regard to the age of the Bovey Tracey lignite, independent 

 palseobotanical evidence supported the Author's suggestion that it 

 was older than had hitherto been thought, but Mrs. Reid considered 

 that our knowledge was not yet sufficient to place it definitely. 



Dr. F. A. Batheb, in congratulating the Author on a paper of 

 remarkable interest most lucidly presented, enquired why a genus 

 with so many species was called 'monotypic' The details of the 

 evolution suggested many thoughts ; he would ask only whether 

 the Author could suggest any adaptive cause of the continuous- 

 changes. 



The Author replied that the word ' monotypic ' was used as 

 applied by botanists to the recent plant, of which there was only 

 one living species, S. aloides, and that, so far as one could judge, 

 there was no special adaptive purpose served by the evolutionary 

 changes described in the fossils. 



With regard to the Glacial Period, Stratiotes could furnish no 

 new evidence : there was no decided break in the evolutionary 

 series, and S. aloides, at any rate, was of little value as an index 

 of climate, since it ranged from beyond the Arctic circle into 

 Central Europe. 



In using the term ' Preglacial ' in the case of the fossils from 

 the Cromer Eorest-Bed, from Eime (near Hanover) > and from 

 Copenhagen, the Author had adopted the chronology of the late 

 Mr. Clement Reid and of those foreign geologists who had made 

 a special study of the beds concerned. 



