EUASTKUM. 31 



the isthmus. Vertical view elliptic, with rounded 

 poles, slightly inflated in the middle on each side. 



Zygospore unknown. 



Length 56-60 ^ ; breadth 40-41 ju, ; breadth of apex 

 19-21 |u ; breadth of isthm. 9'6-12 /* ; thickness 26-28 p. 



SCOTLAND. Xear Cambus-o'-May, Aberdeen : G-len 



e.' j 



Cloya, Forfar ; Glen Coe, Argyll (Roy $ m Biss^ft). 

 Ehiconich, Sutherland ! 



IEELAND. Connemara, G-alway (ArcJter). 



Geocjr. Distribution. Finland. United States. 



17. Euastrum insigne Hass. 

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



Euastrum insigne Hass. Brit. Freshw. Alg. 1845, p. 21, t. 91, f. 2 ; Ealfs, 



Brit. Desm. 1848, p. 83, t, 13, f. 6 ; Arch, in Pritch. Infus. 1861, p. 729, 



t. 3, f . 12 ; Babenk. Flor. Em-op. Algar. Ill, 1868, p. 184 ; Kirolm. Alg. 



Schles. 1878, p. 158 ; Cooke, Brit, Desru. 1886, p. 69, t. 33, f. 4 ; Hansg. 



Prodr. Algenfl. Bohin. 1888, p. 206 ; De Toni, Syll. Alg. 1889, p. 1092 ; 



West, Alg. N. Wales, 1890, p. 287 ; Alg. W. Ireland, 1892, p. 137 ; Alg. 



Eng. Lake Distr. 1892, p. 722 ; Eoy & Biss. Scott. Desui. 1893, p. 177 ; 



West G. S. West, Some N. Amer. Desm. 1896, p. 242 ; Nordst. Index 



Desm. 1896, p. 147 ; West & G. S. West, Alg. S. England, 1897, p. 483 ; 



Alga-fl. Yorks. 1900, p. 62 ; Alg. N. Ireland, 1902, p. 28. 

 Didymidium (Euastrum) insigne Eeinsch, Algenfl. Franken, 1867, p. 130. 

 Euastrnm mammillosum Wolle in Bull. Torr. Bot. Club. 1883, p. 18, t. 27, 



f . 21 ; Desm. U. S. 1884, p. 102, t. 26. f. 14, 15 (figures bad) ; De Toni, 



Syll Alg. 1889, p. 1078. 



E. insigne b. typicum Eacib. Nonn. Desm. Polon. 1885, p. 92. 

 E. insigne c. montanum Eacib. 1. c. t. 13, f. 1. 

 Helierella insignis Kuntze, Eevis. gen. plant. 1891, p. 898. 

 H. mammillosa Kuntze, 1. c. p. 899. 

 Euastrum insigne var. elegans Schmidle Beitr. Alg. Schwarzwald. 1893, 



p. 105, t. 6, f. 7, 8. 

 E. insigne var. mammillosum (Wolle) Turn. Freshw. Alg. E. India, 1893, 



p. 79. 



Cells of medium size, about twice as lono' as broad, 



. 



deeply constricted, sinus widely open, narrowed towards 

 the extremity ; semicells widely deltoid in the basal 

 portion, then narrowed into a neck, which widens 

 again into an obyersely-deltoid apex, basal and apical 

 angles rounded, frequently with an undulation on the 

 margin just aboye the basal angle, apex truncate with 

 a narrow median incision ; semicells with a large, sub- 

 mamillate, downwardly-directed protuberance within 



