246 BRITISH DESMIDIACE^E. 



semicell, with a central pyrenoid. Filaments twisted, 

 with or without a mucous sheath. 



Zygospore unknown. 



Length 25 '5-28 p ; breadth 32'5-38'5M, : breadth of 

 isthmus 23-28*5 [JL ; breadth of apices 21-25'5^. 



SCOTLAND.- -Plankton of Loch Fadaglioda. Lewis, 

 Outer Hebrides ! 



Geogr. Distribution. Brazil. 



This species, although occurring abundantly in the plankton 

 of Loch Fadaghoda, has not been observed from any other 

 locality in Britain. It is distinguished from D. Swartzii by the 

 proportionately greater length of its cells, and by the shortened 

 and more rounded lateral angles of the semicells. The vertical 

 view is likewise more robust, and the sides are convex (not con- 

 cave as in D. Swartzii). There is usually no trace of a space 

 between the apices of adjacent cells, but it may sometimes be 

 detected with high magnification. 



4. Desmidium Swartzii Ag. 

 (PL CLXIII, figs. 5-8.) 



Diatoma Sivartzii Agardh, Disp. A]g. 1812, p. 38. 



Desmidium Sicartzii Agardh, Syst. Alg. 1824, p. 9; Grev. Scott. Crvpt. 

 Fl. 1827, v. 5, t. 292, v. 6, p. 32 ; in Hook. Brit. Fl. 1833, p. 402 ; Ktitz. 

 Synops. Diat. 1834 : p. 85 (sep.); Breb. Alg. Falaise, 1835, pp. 53, 267, 

 t. 2, 5 ; Menegh. Synops. Desm. 1840, p. 203 ; Ralfs in Ann. Mag. Nat. 

 Hist. v. 11, 1843, p. 375, t. 8, f. 3 ; ibid. v. 15, 1845, p. 405 ; Hass. Brit. 

 Freshw. Alg. 1845, p. 344, t. 83, f. 7, 8 ; Kiitz. Phyc. Germ. 1845, p. 141 ; 

 Ralfs, Brit. Desm. 1848, p. 61, t. 4 ; Kiitz. Spec. Alg. 1849, p. 190 ; Nag. 

 Gatt. einz. Alg. 1849, p. 131, t. 8 D ; Breb. Liste Desm. 1856, p. 119; 

 De Bary, Conj. 1858, p. 76, t, 6, f. 57 ; Arch, in Pritch. Inf. 1861, p. 723 ; 

 Rabenh. Krypt.-fl. Sachs. 1863, p. 180; Reinsch, Alg. Frank. 1867, 

 p. 205 ; Rabenh. Flor. Europ. Alg. 1868, p. 154 ; Delp. Spec. Desm. 

 subalp. 1873, p. 56, t, 2. f. 8-20 ; Kirchn. Alg. Schles. 1878, p. 132 ; 

 Gay, Monogr. loc. Conj. 1884. p. 80. t, 3, f. 3 ; Wolle, Desm. U. S. 1884, 

 p. 26, t. 2, f. 1-5 ; Cooke, Brit, Desm. 1887, p. 10, t. 5, f. 2 ; Hauptfl. 

 Zellm. u. Hiillgallerte Desm. 1888, p. 191, t. 2,f. 1-5. 7-9 ; Hansg. Prodr. 

 Alg. Bohm. 1888, p. 171 ; Nordst, Freshw. Alg. N. Zealand, 1888, p. 25; 

 De Toni, Svll. Alg. 1889. p. 780 ; West, Alg. N. Wales, 1890, p. 7 (sep.) ; 

 Alg. W. Ireland, 1892, p. 117 ; Alg. Engl. Lake Distr. 1892, p. 7; Roy 

 & Biss. Scott. Desm. 1893, p. 9 (sep.) ; West & G. S. West, Alg. S. Eng- 

 land, 1897, p. 497 ; Comere, Desm. de France. 1901, p. 200, t. 16, f. 11 ; 

 West & G. S. West, Alga-fL Yorks. 1902, p. 110 : Alg. N. Ireland, 1902, 

 p. 59 ; G. S. West, Brit. Freshw. Alg. 1904, p. 178, f. 69 A ; West & G. S. 

 West, Alg. Burma, 1907, p. 226 ; Georgev. Desm. Wlasina See, 1909, 

 p. 190 ; Desm. Macedonia, 1910. p. 237 ; Hustedt, Desm. et Bacill. Tirol, 

 1911, p. 342 ; Kaiser, Alg. Traunst, u. Chiem. 1914, p. 154. 



