230 BRITISH DESMIDIACE^E. 



Hyalotltcca dissiliens (8m.) Breb. in Ralfs, Brit. Desm. 1848, p. 51, t. 1, 

 f. 1; Breb. Liste Desm. 1856, p. 118; De Bary, Conj. 1858, p. 70; 

 Wallich, Desm. low. Bengal, 1860, p. 187 ; Arch, in Pritch. Inf. 1861, 

 p. 722, t. 2, f. 32, 35 ; Rabenh. Krypt,-fl. Sachs. 1863, p. 179 ; De Notaris, 

 Desm. Ital. 1867, p. 25, t. 1, f. 1 ; Reinsch, Alg. Frank. 1867, p. 203 ; 

 Rabenh. Flor. Europ. Alg. 1868, p. 152 ; Wood, Freshw. Alg. N. Amer. 

 1873, p. 124, t, 12, f. 12 ; Delp. Spec. Desm. subalp. 1877, p. 47 ; Kirchn, 

 Alg. Schles. 1878, p. 131 ; Wille, Ferskv. Alg. Nov. Semlj. 1879, p. .61 ;. 

 Gay, Mono. loc. Conj. 1884, p. 79; Wolle, Desm. U. S. 1884, p. 22, t. 1, 

 f. 3-12, t. 24, f. 26 ; Lagerh. Bidr. Amer. Desm.-fl. 1885, p. 228 ; Cooke, 

 Brit. Desm. 1887. p. 7, t. 3, f. 1 ; Hansg. Prodr. Alg. Bohm. 1888, p. 168 ; 

 Boldt, Desm. Gron. 1888, p. 43, t. 2, f. 53 ; De Toni, Syll. Alg. 1889, 

 p. 785 ; Wille in Engler, Natur. Pflanzenf. 1890, p. 15, f. 9 ; Heinierl, 

 Desm. Alpin. 1891, p. 588; West, Alg. W. Ireland, 1892, p. 116; Ate. 

 E. Lake Distr. 1892, p. 6 ; Roy & Biss. Scott. Desm. 1893, p. 9 ; Liitkem. 

 Desm. Attersees, 1893, p. 538 ; Turn. Freshw. Alg. E. India, 1893, p. 151 ; 

 Borg. Ferskv. Alg. Ost. Gronl. 1894, p. 32; Schroder, Beitr. Alg. Riesen- 

 gebirges, 1897, p. 28 ; West & G. S. West, Alg. S. England, 1897, p. 497 ; 

 G. S. West, Alga-fl. Cambs. 1899, p. 25 ; West & G. S. West, Furth. 

 Contr. Alg. W. Indies, 1899, p. 284 ; Comere, Desm. France, 1901, p. 190, 

 t. 16, f. 7 ; West & G. S. West, Freshw. Chlor. Koh Chang, 1901, p. 97 ; 

 Alg.-fl. Yorks. 1902. p. Ill ; Alg. Ceylon, 1902, p. 195 ; Alg. N. Ireland, 

 1902, p. 60 : Liitk. Zellm. Desm. 1902, p. 365, t, 18, f. 16, 29, 30 ; Borge, 

 Alg. erst. Regn. Exped. II, 1903, p. 122 ; G. S. West, Brit. Freshw. 

 Alg. 1904, p. 176, f. 68, A-D ; West & G. S. West, Freshw. Alg. Orkneys 

 & Shetlands, 1905, p. 28; Alg. Burma, 1907, p. 225, t. 12, f. 11-15; 

 Borge, Botan. Notiser, 1911, p. 203 ; Kaiser, Alg. Traunstein Chiemeau,. 

 1914, p. 153 ; Acton, HyalotJieca dissiliens, 1916. p. 379. 



H. tmicosa Kiitz. Spec. Alg. 1849, p. 187. 



Cells of medium size, about Ij times broader than 

 long; constriction extremely small, consisting of a very 

 slight concavity in the middle of the lateral margins; 

 cells united by their apices to form long slimy filaments, 

 constricted at the joints ; apex of semicells broadly 

 truncate, about as broad as the isthmus, lateral margins 

 slightly convex ; vertical view circular, sometimes with 

 2 opposite papilla?, or 3, equidistant (see formse bidentula 

 and tridentula, infra). Chloroplasts axile, one in each 

 semicell, with a central pyrenoid and a number of radiat- 

 ing ridges, star-like in the vertical view. Filaments 

 usually enveloped in a conspicuous gelatinous sheath, 

 often as broad as the filament itself. 



Zygospores produced after the dissociation of the 

 filaments into isolated cells, spherical or rounded-oblong,, 

 smooth, contained in the swollen conjugation tube, to 

 which the gametangia remain attached. 



Length 10-33(j,; breadth 10-39 pi; diam. zygosp. 

 1 5-25 i. 



