154 BRITISH DESMIDIACEjE. 



Cosmarium ornatiun from the localities in which Ralfs obtained 

 the species, and they are much more in agreement with those 

 obtained from other parts of the British Islands than with 

 that author's figures. Moreover, the British and Swedish 

 specimens differ in no essential points. The creation of 

 varietal names, such as those given by Raciborski, by an 

 author who has not examined the original specimens, is greatly 

 to be condemned. 



Ralfs' figure of the zygospore is similarly not very good. 

 The furcate spines are most probably portrayed too long. 



Eichler and Grutwiiiski have described a G. pseudoornatum 

 (' Nonn. spec. alg. nov/ 1894, p. 170, t. 5, f. 25), in which the 

 apical part of the semicell does not project. 



152. Cosmarium commissurale Breb. 

 (PL LXXVIII, figs. 1 1-14.) 



Heterocarpella commissuralis Breb. in Cliev. microscop. et de leur usage, 



Paris, 1839, p. 272 [name only]. 

 Cosmarium commissurale Breb. in Menegh. Synops. Desni. 1840, p. 220 ; 



Ralfs, Brit. Desm. 1848, p. 105, t, 16, f . 8 ; Ktitz. Spec. Alg. 1849, p. 176 ; 



Breb. Liste Desm. 1856, p. 131 ; Arch, in Pritch. Iiifus. 1861, p. 734 ; 



Rabenh. Flor. Europ. Alg. Ill, 1868, p. 170 ; Wolle, Desm. U. S. 1884, 



p. 83, t. 18, f. 49-51 ; Cooke, Brit. Desm. 1887, p. 113, t. 40, f. 5 ; De Toni, 



Syll. Alg. 1889, p. 1047 ; Roy & Biss. Scott. Desm. 1894, p. 44 ; Nordst. 



Index Desm. 1896, p. 77 ; West & G. S. West, Alg. S. England, 1897, 



p. 491 ; Alga-fl. Yorks. 1900, p. 71 ; Notes Alg. Ill, 1903, p. 75. 

 Euastrum commissurale Wallich, Desm. Low. Bengal, 1860, p. 284, t. 14, 



f. 12-13. 

 Didymidium (Cosmarium) commisurale Reinsch, Algenfl. Franken, 1867, 



p. 120 [forma A]. 

 Ursinella commissuralis Kimtze, Revis. gen. plant. 1891, p. 924. 



Cells small, about 1^ times as broad as long, very 

 deeply constricted, sinus at first narrow and closed, 

 then widely dilated (often subrhomboidal) ; semicells 

 narrowly subreniform with a slightly produced and 

 widely truncate apex ; lateral parts (almost " lobes ") 

 of semicell granulate, with 6-8 granules showing at 

 the margin and 7-10 within the margin, apex with 6-7 

 marginal granules, in centre of semicells with a large 

 granulate protuberance. Side view of semicell trans- 

 versely elliptic with a slightly produced and truncate 

 apex, sides and apex granulate. Vertical view about 

 twice as long as broad, with a large granulate pro- 



