114 BRITISH DESMIDIACEJE. 



narrow, diverging lobules (similar to the processes of 

 the polar lobe) with deeply-furcate apices ; sometimes 

 one or both lateral lobes are simple and undivided. 

 Side view of semicell ovate-lanceolate, apex produced. 

 Vertical view narrowly subrhomboid, with produced 

 and acuminate poles. Cell-wall smooth or finely 

 punctate. 



Zygospore unknown. 



Length 123-195 ju; breadth 11 3-1 86 p, ; breadth of 

 isthmus 17 30ju; breadth of polar lobe (maximum) 

 65-92 fj. ; thickness 27-30 p.. 



WALES. --Capel Curig, Carnarvonshire ! (Cooke $' 

 Wills). Dolgelly, Merioneth (Ralfs). 



SCOTLAND. Plankton of Loch nan Cuinne ! 

 (J. Murray), and of Loch Shin!, Sutherland. Rhi- 

 conich, Sutherland ! Plankton of Loch Fadaghoda, 

 Lewis, Outer Hebrides ! 



IRELAND. Near Lough Magrath, Donegal ! Derry- 

 clare Lough, Glendalough, and small loughs between 

 Clifden and Roundstone, Gal way ! 



Geogr. Distribution.- -France. Germany. Galicia in 

 Austria. Sweden. N. India. Central Africa. United 

 States. Brazil. Paraguay. 



Ralfs, in 1844, described and figured what lie imagined 

 was the same species as Micrasterias melitensis Menegh. The 

 latter was originally described as Euastrum Crux-melitensis 

 by Ehrenberg in 1832, and is now known as Micrasterias 

 Crux-melitensis (Ehrenb.) Hass. 



The first person to recognize that Ralfs' plant was different 

 from M. Crux-melitensis was Hassall, and in his ' British 

 Freshwater Algsd' in 1845 he named it M. radiata. Hassall's 

 description is fairly good, but his figure is wretched. He 

 distinctly states, however, that his name M. radiata is given 

 to the same plant as that described and figured by Ralfs in 

 1844 under the name of M. melitensis. 



In 1848, in his ' British Desmids,' Ralfs placed Micrasterias 

 radiata Hass. and his own M. melitensis as synonyms of 



Micrasterias furcata Ag." Agardh's description of M. furcata 

 (in ' Flora/ 1827, p. 643) is very brief, and reads thus: 



Micrasterias furcata, radiis pluries f urcatis obtusis." From 

 such an imperfect description it is quite impossible to be sure of 



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