160 



BRITISH DESMIDIACEJC. 



Length 26'4-28'S p. ; breadth 25-2-30 p, ; breadth of 

 isthmus 7-10 /u ; thickness 14-4-17 p. 



SCOTLAND.- -Near Ballater, Aberdeen ; G-leii Dye, 

 Kincardine; Rannoch, Perth (Roy fy Bissett). 



IRELAND.- -Lough Machugh, Donegal (abundant) ! 



Geogr. Distribution.- -Germany. Glalicia in Austria 

 (form). Norway. Sweden. Bornholm. Finland. 

 Iceland. Faeroes. Spitsbergen. Uruguay. 



This variety very closely resembles C. subtumidum JSTordst. 

 var. Klebsii (G-utw.) W. & G-. S. West, especially in the front 

 view, but it can be recognized by the protuberance on each 

 side of the vertical view. 



19. Cosmarium tumidum Lund. 

 (PL LX, fig. 18.) 



Cosmarium tumidum Lund. Desm. Siiec. 1871, p. 45, t. 3, f. 16 ; Wolle, 



Desni. U.S. 1884, p. 61, t. 15, f. 23 ; Boldt, Desm. G-ronland, 1888, p. 15 ; 



De Toni, Syll. Alg. 1889, p. 955 ; West, Alg. N. Wales, 1890, p. 288 ; 



Alg. Eng. Lake Distr. 1892, p. 725 ; Roy & Biss. Scott. Desm. 1894, 



p. 177 ; Nordst, Index Desm. 1896, p. 262. 

 C. pseudonitidulum Nordst. var. majus E-eiiiscli, Contrib. Alg. et. Fung. 



1875, p. 88, t. 12, f. 7. 

 Ursinella tumida Knntze, Eevis. gen. plant. 1891, p. 926. 



Cells rather small, a little longer than broad, deeply 

 constricted, sinus narrow, widening outwards; semi- 

 cells subsemicircular- elliptic, apices broadly convex. 

 Side view of semicell circular. Vertical view elliptic - 

 rhomboid, widely tumid at the middle on each side, 

 ratio of axes about 1 : 1*35. Cell-wall finely punctate, 

 punctulations larger in the centre of the semicells. 

 Chloroplasts axile, each with one pyrenoid. 



Zygospore unknown. 



Length 33-37 /*; breadth 27-32 /u; breadth of isthmus 

 8-9 -5 // ; thickness 23 ju. 



WALES.- -Capel Curig, Carnarvonshire! 



SCOTLAND. - Slewdrum, Upper Powlair, Aboyne, 

 Castletoii, and Glen Clunie, Aberdeen ; near Menmuir, 

 Forfar; Folotry, Perth (Roy ^ Bissett). 



IRELAND.- -Near Oughterard, Galway ! 



Geogr. Distribution. France. Germany (form). 



