146 BRITISH DESMIDIACE.^. 



the cell, yellowish-brown in colour ; cHoroplasts with 

 distinct ridges and scattered pyrenoids; terminal 

 vacuoles with many moving granules. 



Zygospore unknown. 



Distance between apices (length) 294-400 /x ; breadth 

 48-64 ju; breadth near apices 10-11 /x. 



ENGLAND. Adel Bog (Turn IT), Cam Fell, and Boston 

 Spa, W. Yorks ! Pilmoor, IS!". Yorks! Dernford Fen, 

 Sheep's Green, and Wimpole Park, Cambridge ! Esher 

 West-end Common, and Frogit Heath, Surrey ! Wool- 

 ton Pond, Hants (Roy). 



SCOTLAND. Near Brin, Inverness ; Bourtie, Aber- 

 deen ; Loch of Park, near Crathes, Kincardine ; Athole 

 Forest, near Loch Mharc, and E. of Falar, Perth (li<>// 

 fy Bissett). 



IRELAND. Loughs Akibbon and Gar tan, Donegal ! 

 Bog near lake at Toome, Antrim ! 



Geogr. Distribution. Austria and Galicia. Italy. 

 Spain. Norway. Sweden. 



This species differs from Cl. Ehrenlergii only in its coloured 

 and striated cell-wall, and in its somewhat smaller dimen- 

 sions. Lundell states that it also differs from CL Hlir<'>tl>rr</!i 

 in its less prominent ventral inflation and in its less obtuse 

 apices, but we find these features very variable in both 

 species. 



The striolation of the cell- wall is very delicate and apt to 

 be at first sight overlooked. 



26. Closterium acerosum (Schrank) Ehrenb. 

 (PI. XVIII, figs. 2-5.) 



Vibrio acerosus Schrank, 1803. 



Bacillaria acerosa Schrank, 1823. 



Closterium acerosum (Schrank) Ehrenb., 1828 ; Infus. 1838, p. 93, t. 2, 



f. xv, t. G, f . i, t. 22, f . v ; Meneg-h. Synops. Desm. 1840, p. 233 ; Hass. 



Brit. Freshw. Alg. 1845, p. 374, t. 87, f. 5 ; Ealfs, Brit. Desm. 1848, p. 



164, t. 27, f. 2; De Bary, Conj. 1858, p. 51 ; Arch, in Pi-itch. Iiifus. INiil, 



p. 747; Rabenh. Flor. Europ. Algar. Ill, 1868, p. 128; Kirchii. Alg. 



Schles. 1878, p. 138; Wolle, Desm. U.S. 1884, p. 41, t. 6, f. 7, 11, 1, s, 



f. 17 ; Cooke, Brit. Desm. 1886, p. 20, t, 9, f . 1 ; Hansg. Prodr. Algenfl. 



Bohm. 1888, p. 179 ; De Toni, Syll. Alg. 1889, p. 824 ; Roy & Biss. Scott. 



Desm. 1894, p. 242 ; Nordst. Index Desm. 1896, p. 37 ; West & G. S. 



West, Alg. S. England, 1897, p. 481 ; Alga-fl. Yorks. 1900, p. 52 ; Freshw. 



Chlorophy. Koh Chang, 1901, p. 164, t. 2, f . 5 , Alg. N. Ireland, 1902, p. 23. 



