86 BEITISH DESMIDIACEJE. 



have only observed it from the plankton. It sometimes 

 exceeds the dimensions of the typical form, and often occurs 

 abundantly in the plankton of the British lakes. 



105. Cosmarium impressulum Elfv. 

 (PL LXXII, figs. 14-18.) 



Cosmarium Menegliinii Breb. forma Eeinsch, Contrib. Alg. et Fung. 1875,. 



t. 12, f. 12 a, 6. 



C. Meneghinii Breb. /3 simplicissimiim "\Ville, Norges Ferskv. Alg. 1880, p. 

 30, t. 1, f. 11 a 1 [not fig-. 11 a] ; Nordst, Freshw. Alg. N. Zeal. 1888, p. 

 58; De Toni, Syll. Alg. 1889, p. 938; West, Desm. Maine, 1888, p. 339; 

 Alg. N. Wales, 1890, p. 289 ; G-utw. Flor. glonow Galic, 1892, p. 125 ; 

 West & G. S. West, Wehv. Afric. Freshw. Alg. 1897, p. 37 ; Schmidt, 

 Grundl. Algeiifl. Liineburg. Heide, 1903, p. 35. 



C. impressulum Elfv. Anteck. Finska Desm. 1881, p. 13, t. 1, f. 9; Eoy & 

 Biss. Jap. Desm. 1886, p. 195, t, 268, f . 10 ; Haiisg. Prodr. Algeiifl. Bohm, 

 1888, p. 248; De Toni, Syll. Alg. 1889, p. 840; Heimerl, Desm. alp. 

 1891, p. 599 ; West, Alg. W. Ireland, 1892, p. 147 ; Alg. Eiigl. Lake 

 Distr. 1892, p. 726 ; Roy & Biss. Scott, Desm. 1894, p. 104 ; Johnson, 

 Bare Desm. U. S. I, 1894, t. 211, f. 6 ; Schmidle, Beitr. alp. Alg. 1895, 

 p. 388 ; Nordst, Index Desm. 1896, p. 143 ; West & G. S. West, Alg. S. 

 England, 1897, p. 487 ; G. S. West, Alga-fl. Cambr. 1899, p. 216 ; West 

 & G. S. West, Alga-fl. Yorks. 1900, p. 92 ; Alg. N. Ireland, 1902, p. 35 ; 

 G. S. West, W. Indian Freshw. Alg. 1904, p. 285 ; West & G. S. West, 

 Further Contrib. Freshw. Plankton Scott. Lochs, 1905, p. 484. 



Euastmm (Cosmarium) impressulum Gay, Monogr. loc. Coiij. 1884, p. 61. 



Cosmarium Meneghinii Breb. forma Reinschii Istvanffi, Diag. prsev. Alg. 

 nov. Hungar. 1887, p. 237 ; Gutw. Flor. glonow Galic, II, 1890, p. 12 ; 

 Borge, Bidr. Siber. Chlor. 1891, p. 12, t. 1, f . 8 ; Gutw. Flor. glonow 

 Galic, III, 1892, p. 125 ; Borge, Siissw. Chlor. Archaiig. 1894, p. 27, t. 2, 

 f . 26 ; Borg. Ferskv. Alg. Ostgronl. 1894, p. 16 ; Borge, Austral. Siiss- 

 wasserchlor. 1896, p. 24; Trop. u. subtrop. Siissw.-Chlor. 1899, p. 22; 

 Susswasseralgen Siid-Patagon. 1901, p. 25 ; Bohlin, Flor. Algol, d'eau 

 douce d. Acores, 1901, p. 69; Borg. Freshw. Alg. Faeroes, 1901, p. 224; 

 Borge, Alg. erst, Eegiiell. Exped., II. Desmid. 1903, p. 98; Alg. Argen- 

 tina u. Boliv. 1906, p. 7. 



Ursinella impressula Kuntze, Eevis. gen. plant. 1891, p. 925. 



Cosmarium crenulatum (Ehreiib.) Breb. var. Reinschii Schmidle, Beitr. 

 Algeiifl. Schwarzwald. u. Eheineb. 1893, p. 96, t. 4, f . 10 ; Schroder, Alg. 

 Versuchsteiche Schles. Fischereiv. Trachenberg. 1897, p. 27. 



C. subortogonum Eacib. "forma minor creiiis minoribus" Borge, Algo- 

 logische Xotizen, 5 (in 'Bot. JSTotis/) 1900, p. 4 (sep.), cum fig. 2. 



C. Meneghinii formae Him, Desm. Finland, 1903, t, 1, f. 6 (?) et 7. 



Cells rather small, about 1-| times as long as broad, 

 deeply constricted, sinus narrowly linear with a slightly 

 dilated apex ; semicells semi-elliptic or subsemicircular, 

 margin regularly and markedly 8-undulate (sometimes 

 almost crenate) ; crenations (including basal angles) 

 equal, two at the apex and two on each of the convex 

 sides. Side view of semicell broadly elliptic or elliptic- 

 subcircular. Vertical view elliptic, ratio of axes about 



