98 BRITISH DESMIDIACEJE. 



Ealfs, Brit. Desm. 1848, p. 209 ; Arch, in Pritch. Infus. 1861, p. 727 ; 



Eabenh. Flor. Europ. Alg. Ill, 1868, p. 193 ; Kirchn. Alg. Schles. 1878, 



p. 163 ; Eoy & Biss. Jap. Desm. 1886, p. 193, t. 268, f . 13 ; Cooke, Brit. 



Desm. 1887, p. 186, t. 48, f. 1 ; Nordst. Bornh. Desm. 1888, p. 187 ; 



Heimerl, Desm. alp. 1891, p. 602 ; West & G. S. West, Some N. Amer. 



Desm. 1896, p. 240 ; Nordst. Index Desm. 1896, p. 48. 

 Didymidium (Micrasterias) apiculatum Eeinsch, Algenfl. Frank. 1867, 



p. 145. 

 Micrasterias fimbriata Ealfs forma apiculata Wolle, Desm. U. S. 1884, 



p. 110. 

 Helierella apiculata Ktintze, Eev. gen. plant. 1891, p. 898. 



Cells large, a little longer than broad, subelliptic in 

 outline, very deeply constricted, sinus widely open out- 

 wards but linear towards its apex ; semicells 5-lobed ; 

 polar lobe distinctly exserted, lower portion with sub- 

 parallel sides, upper portion widely dilated, apex retuse- 

 emarginate, angles with a pair of diverging spines and 

 with a large curved spine on the apical margin close to 

 each angle, and with a pair of spines on each side of the 

 apical notch ; lateral lobes subequal, bilobulate, lobules 

 again divided and each division furnished with two 

 (sometimes three) marginal curved spines ; incisions 

 bordering the polar lobes opening widely outwards, the 

 remaining incisions (both primary and secondary) more 

 or less open. Side view narrowly ovate-pyramidate 

 with a truncate apex bearing spines. Vertical view 

 rhomboid-elliptic with acute poles. Cell- wall furnished 

 with numerous minute spines, arranged in subradiate 

 rows or scattered over the surface, with four rather 

 larger spines arranged in a quadrate manner in the 

 middle of each semicell just above the isthmus. 



Zygospore unknown. 



Length 220-294 /i; breadth 180-250 p.; breadth of 

 isthmus 30-36 /x,. 



ENGLAND. Bowness, Westmoreland (Turner}. 



Geogr. Distribution. - - France. Germany. Galicia 

 in Austria. Italy. Sweden. Denmark. Bornholm. 

 Finland. Poland. Russia. Japan. India. Burma. 

 United States. 



This beautiful species in its typical form is only known 

 from the English Lake District, having been found by 

 Turner in a locality which furnishes numerous specimens of 



