COSMARIUM. 151 



Cells smaller, broadly elliptic, about 1J times as 

 long as broad ; semicells subsemicircular, with 13 or 

 14 crenations in the margin. 



o 



Zygospore globose, furnished with long spines (or 

 processes) with tridentate apices. 



Length 32-43 JJL; breadth 27-36 p.; breadth of isth- 

 mus 10-13'5/x; diam. zygosp. without spines 34 /x, 

 with spines 44-45 /*. 



ENGLAND.- -Near Bristol, Gloucestershire (Rolfs). 



IEELAND. Xear Oughterard, Gal way ! 



Geogr. Distribution. United States. 



This variety is distinguished from all the other forms of 

 C. undulatum by the crenation of the margin, which is of 

 precisely the same nature as that of Gosmarium speciosum 

 Lund. The semicells are not inclined to be subquadrate as 

 in var. minutum and var. crenulatum. 



The zygospore of C. undulatum figured by Ralfs in his 

 ' British Desmids/ t. 15, f. 8, most certainly belongs to this 

 variety. The empty semicells which he figures round the 

 zygospore are crenate. 



13. Cosmarium subundulatum Wille. 

 (PL LIX, figs. 13-15.) 



Cosmarium undulatum (Corda) Kalfs var. tumidum Jacobs. Desni. Danem. 



1876, p. 197, t. 8, L 18 ; Borge, Chlor. Norska Finmark. 1892, p. 10, 



t. 1, f. 8. 

 Cosmarium subundulatum Wille, Norges Ferskv. Alg. 1880, I, p. 27, t. 1, 



f . 9 ; Boldt, Desm. Gronl. 1880, p. 17 ; Be Toni, Syll. Alg. 1889, p. 1051 ; 



Roy & Biss. Scott. Desm. 1894, p. 175 ; West & GK S. West, Alga-fl. 



Yorks. 1900, p. 81. 



Ursinella subundulata Ktintze, Kevis. gen. plant. 1891, p. 925. 

 Cosmarium Nuttallii West, Alg. W. Ireland, 1892, p. 151, t. 21, f. 5. 

 C. undidatum Corda var. subundulatum Borg. Fresliw. Alg. Ostgronl. 1894, 



p. 17, t. 1, f. 8 ; Schmidle, Alg. aus Sumatra, 1895, p. 303, t. 4, f . 9. 



Cells of moderate size, 1J times longer than broad, 

 elliptic, deeply constricted, sinus very narrow, dilated 

 at the apex; semicells semi-elliptic, basal angles 

 rounded, apex commonly a little flattened, margins 

 with about 12 undulations, and with two series of 

 undulations within the margin corresponding to the 

 peripheral ones. Side view of semicell ovate, apex 



