184 BRITISH DESMIDIACE-3E. 



Length 24-35 ju; breadth 18'5-21'5ju; breadth of 

 isthmus 7-7*5 ju ; thickness H-12'5//,; diam. zygosp. 

 without spines 30 /i, with spines 46 /x. 



SCOTLAND. Harris, Outer Hebrides ! 



Geogr. Distribution. United States. 



In the zygospore we examined (from the United States) the 

 apices of the spines were simple, but Wolle has figured a 

 zygospore in which the spines are furcate. 



Var. Hibernicum Cooke. 



C. Hammeri forma, Crowe in Quart. Journ. Micr. Sci. 1873, p. 435. 

 C. Hammeri var. Hibernicum Cooke, Brit. Desm. 1886, p. 81. 



Cells about 1^- times longer than broad, apices 

 convex-truncate ; in the side view with a minute tooth- 

 like protuberance visible at the constriction. 



IRELAND. Arklow, Co. Wicklow (Crowe). 



38. Cosmarium Nymannianum Grim. 

 (PI. LXII, figs. 26, 27.) 



Cosmarium Nymannianum Grim, in Rabeiih. Flor. Europ. Alg. Ill, 1868, 

 p. 166 ; Lund Desm. Suec. 1871, p. 36, t. 3, f. 1 ; Wolle, Desm. U. S. 

 1884, p. 79 ; Cooke, Brit. Desm. 1886, p. 82, t. 36, f . 1 ; De Toiii, Syll. 

 Alg. 1889, p. 964 ; West, Alg. W. Ireland, 1892, p. 142 ; Alg. Eng. Lake 

 Distr. 1892, p. 724 ; Roy & Biss. Scott. Desm. 1894, p. 169 ; Nordst. 

 Index Desm. 1896, p. 184 ; West & O. S. West, Alg. S. England, 1897, 

 p. 485; Alga-fl. Yorks. 1900, p. 78; Alg. N. Ireland, 1902, p. 32; 

 Freshw. Alg. Ceylon, 1902, p. 161. 



Ursinella Nymanniana Kiintze, Eevis. gen. plant. 1891, p. 925. 



Cells rather small, elongate-subhexagonal, about 1-J 

 times longer than broad, deeply constricted, sinus 

 narrowly linear with a dilated extremity; semicells 

 truncate-pyramidate, basal angles rounded, lower half 

 of sides convex, upper half concave, upper angles 

 rounded, apex retuse, in the centre with a large and 

 conspicuous scrobiculation. Side view of semicell 

 subcircular. Vertical view subrhomboid-elliptic, at the 

 middle on each side thickened and showing the large 

 scrobiculation, ratio of axes about 1 : 1*8. Cell-wall 

 distinctly punctate. Chloroplasts axile, each with one 

 pyrenoid. 



Zygospore unknown. 



