Ifi6 



Notes on Diatomacearum Dillwynii, or The Genera and 

 Species of Diatomace.t: in " The British Conferyj: ' 



OF DlLLWYN. 



By F. Kitton, Hon. F.R.M.S., Mem. Cor. Soc. Beige de Mic. 



(Read November 24, 1882.; 

 PLATE VI. 



The few forms belonging to the class Diatomaceae figured and 

 described by L. W. Dillwyn in his " British Conferva? " (4to, 1809) 

 comprise only the filamentous species. Being unacquainted with their 

 siliceous character and other important differences which distin- 

 guish the DiatomaceaB from all other algoicl forms, he placed them 

 among the Confervas (a genus to which the early botanists seem 

 to have relegated all the " water- weeds ") on account of their 

 filamentous growth and "jointed" appearance, caused by the 

 cohesion of the frustules, and which he considered analogous to 

 those in what we now call Oscillaria?, &c. He, however, recog- 

 nises Decandolle's genus Diatoma. 



Having had the opportunity, through the kindness of Dr. M. C. 

 Cooke, of examining Dillwyn's own specimens, I am able to refer 

 them to the genera and species in which these forms are now 

 placed. 



Diatoma, Decandolle. — Plantse pseudo-parasitica oculo nudo vix 

 conspicuas, filamentis simplicibus articulatis, articulus in adulta 

 planta transversum sectis. 



The species, arranged in the section ArticuJa solutis of my 

 " Synopsis," constitute a natural family, and may be referred to this 

 genus. 



Conferva striatula. — C. filis simplicibus compressis dilute viridi- 

 bus dissepimentis alternatim solutis, articulis diametro vix breviori- 

 bus transversis striatis (E. B., t. 1,928). 



On Fuci and Conferva, in the Sea at Cromer (=Hhabdonema 

 arcuatum, F. K.). 



C.jlocculosa. — C. filsementis sub-simplicibus, compressis, minutis, 



