HYALOTHECA. 235 



2. Hyalotheca mucosa (Mert.) Ehr. 

 (PI. CLXII, figs. 1-4.) 



Conferva mucosa Mert. in Dilhvyn Brit. Conferva?, 1809, p. 46, t. B ; Aaardh, 



Syst. Alg. 1824, p. 90 : Harv. in Hook. Br. Fl. 1833, p. 351. 

 ?? Actinocydus rariabilis Corda in Aim. de Carlsbad, 1840, p. 198, t. ii, 



f. 11-14. 

 Hyalotheca nuicosa Ehr. in Berlin Monatsb. 1840. p. 212; Ralfs, Brit. 



Desm. 1848, p. 53, t. 1. f. 2 ; Arch, in Pritch. Inf.' 18(51. p. 722 ; IJabenh. 



Krypt.-fl. Sachs. 18(33, p. 179 : De Xot. Desm. Ital. 18(37, p. 26, t. 1, f. 2 ; 



Reinsch, Alg. Frank. 1867, p. 204 ; Rabenh. Flor. Europ. Alg. 1868 r 



p. 152 ; Xordst. Xorges Desm. 1873, p. 48 ; Wood, Freshw. "Ate. N. 



Amer. 1873, p. 124 ; Kirchn. Alg. Schles. 1878, p. 131 ; Lagerh. Bidr. 



Sverig. Desm. 1883, p. 54 ; Gay, Monogr. loc. Conj. 1884, p. 79, t. 3, f. 2 ; 



Wolle, Desm. U. S. 1884, p. 23/t. 1, f. 13 : Hacib. Xon. Desm. Polon. 1885, 



p. 64 ; Lagerh. Bidr. Amerik. Desm. 1885, p. 228 : C'ooke. Brit. Desm. 



1887, p. 8, t. 3, f. 2 : Hansg. Prodr. Alg. Bohm. 1888, p. 168 ; Hauptfl. 



Zellm. u. Hulteallerte Desm. 1888, pp. 63, 104; De Toni, Syll. Ate. 



1889, p. 787 ; West, Alg. X. Wales, 1890, p. 7 ; Alg. Engl. Lake Distr. 



1892, p. 6; Ate. \V. Ireland, 1892, p. 117; Roy & Biss^ Scott. Desm. 



1893, p. 9 ; West & G. S. West, Ate. S. England, 1897, p. 497 ; Borge, 

 Siissw. Alg. S. Pataffon. 1901, p. 17 :" West & G. S. West. Alga.fl. York*. 

 1902, p. Ill; Alg." Orkneys and Shetland*, 1905, p. 28; Alg. Third 

 Tanganyika Exped. 1907, p. 131, t. 4, f. 4. 5 : Alg. Burma. 1907, p. 22i. 



Gloeoprium nnicosuni Ralfs in Ann. MaL r . Xat. Hist. v. 16, 1845, p. 11, t. 3, 



f. 6 : Hass. Brit. Freshw. Ate. Is45. p. :U7, t. 83. f. 5, 6. 

 Hyalotheca Ralfsii Kiitz. Spec. Ate. 1.S49. p. 1S7. 

 Mixot(''/tin//t anniUare Delj). Spec. Desm. subalp. 187."). p. 50, t. I, f. 13-19. 



Cells of medium size, quadrangular, about as long as 

 broad, or sometimes rather longer, cylindrical, usually 

 without the faintest indication of a constriction in the 

 normal resting cell, very slightly or not conspicuously 

 constricted at the joints, each semicell with 2 parallel 

 rings of tiny granules just beneath its apex ; vertical 

 view circular ; chloroplasts axile, one in each semicell, 

 each with a central pyrenoid and several radiating ridges; 

 filament enclosed in a very massive gelatinous sheath, 



/ 



usually of greater thickness than in H. (lissiliens. 



Zygospore spherical, or oblong with rounded ends, 

 membrane smooth and yellowish brown. 



Length 16-22 pi; breadth 16-22^; diam. zygosp. 

 27-30 pi. 



ENGLAND. Plankton of Ennerdale Water, Cumber- 

 land ! Westmoreland, and in the plankton of Brother's 

 Water, Grasmere, and Coclale and Easedale Tarns! 

 W. and X. Yorks ! Essex and Herts (Hassall). War- 



