203 



On Some Desmids N"ew to Britain in 1880. 



By M. C. Cooke, M.A., LL.D., F.L.S. 



{Rea^l Odooer 227id, iSSO.) 

 Plates XIII, XIV, XY, XVI. 



My first intention was merely an enumeration of tlie D,;smi(Uce 

 found in the British Islands, and especially in England and Wales 

 during the year now drawing to a close. This seemed to be so un- 

 interesting a method of sj^ending an evening, that I resolved upon a 

 more detailed account of some of the species belonging to one genus, 

 hoping by this means to secure greater concentration, and to impart 

 more clear and distinct views than by the former method. 



I must premise that I am indebted to my friend, Mr. A. W. 

 Wills, of Birmingham, for a knowledge of the species to be intro- 

 duced to you as British species. A splendid gathering made by 

 him at Capel Curig afforded a large number of species not before 

 recorded in England or Wales, although some of them had been 

 found in Ireland. Only a portion of the new species need be men- 

 tioned, as I purpose confining my remarks solely to the genus 

 Staurastrum. Others may find a place in an AjDpendix. 



It is unnecessary to introduce the subject by informing an 

 audience like the present of the nature and affinities of the Des- 

 imdice. I take it for granted that all microscopists are acquainted, 

 cursorily at least, with these interesting little plants ; that they 

 form a portion of fresh-water Algte, are characterized by a green 

 endrochrome and absence of silex, in which features they differ from 

 the Diatomacece. 



Most of you are aware that Desmids are found only in fresh 

 water, and that the majority prefer clear to stagnant pools or run- 

 ning streams. 



Desmids consist of but a simple cell, which is usually more or less 

 constricted, and divisible in the centre into two equal and symme- 

 trical halves. 



A portion of the numerous genera is characterized by a greo-a- 



