part 2] GEOLOGICAL HISTORY OF THE GENUS STRATIOTES. 117 



5. The Geological History of the G-enus Stratiotes: an 

 Account of the Evolutionary Changes which have 

 occurred within the Genus during Tertiary and Qua- 

 ternary Times. By Miss Marjorie Elizabeth Jane 

 Chandler. (Communicated by Mrs. E. M. Held, B.Sc, 

 F.L.S., F.G.S. Bead April 12th, 1922.) 



[Plates V & VI.] 



I. Introduction. 



Stratiotes aloides, the Water-Soldier or Water-Aloe, is a well- 

 known monotypic European and Siberian plant of the Mono- 

 cotyledonous family Hydrocharitacese ; palseontological studies of 

 recent years have shown this plant to be the sole survivor of an 

 ancient genus which was living far back in the Tertiary Era. 



II. History op Pal^obotanical Investigation. 



The principal land-marks in the paheobotanical study of Stratiotes 

 are as follows : — 



1, 1822. The description of Carpolithes thalictroides Adolphe 

 Brongniart; var. parisiensis (Paris Basin); var. websteri (New- 

 port, Isle of Wight) (2).i 



2, 1833. Description of a second species, Folliculites Icalten- 

 nordheimensis Zenker, and the suggestion that Brongniart's fossils 

 belonged to this genus (7). 



3, 1892. Description of a third species, Faradoxocarpus cari- 

 natus Nehring, from Pleistocene beds (33). 



1, 1892, later. Recognition that Nehring's Paradoxocarpus 

 was a species of Folliculites of Zenker, by Potonie (36). 



5, 1896. Identification of Folliculites as Stratiotes by Keilhack 

 (54, 56), F. carinatus being synon} r mous with S. aloides Linn, and 

 F. Icaltennordheimensis being an extinct species. 



Apart from these points, the whole literature of the subject is 

 a mass of controversy. The confusion has been increased by the 

 fact that S. websteri and F. Icaltennordheimensis had been in- 

 adequate^ figured and described ; while, owing presumably to a 

 strong generic resemblance, shown by the figures (which failed, 

 nevertheless, to make clear the specific distinctness), the two 

 names were frequently used as synonyms. The disorder occasioned 

 could not be cleared up by an appeal to type-specimens, for, in the 

 case of Stratiotes websteri, these, and the type-locality too, were 

 lost. Moreover, other species had also become involved in the 

 chaos under one or both of the two names. 



1 Numbers in parentheses refer to the Bibliography, § IX, p. 133. 



Q. J. G. S. No. 314. k 



