250 BRITISH DESMIDIACE^. 



Nat. Hist. v. 11, 1843, p. 373, t. 8, f. 1 ; Hass. Brit, Freshw. Alg. 1845, 

 p. 342, t. 83, f. 1, 2 ; Kirchn. Alg. Schles. 1878, p. 132 ; Wolle, Desm. 

 U. S. 1884, p. 25, t. 3, f. 1-4, t. 24, f. 25 ; Cooke, Brit. Desm. 1887, p. 9, 

 t. 4, f. 2 ; Hansg. Prodr. Alg. Bohm. 1888, p. 172 ; De Toiii, Syll. Alg. 

 1889, p. 783; West, Alg. W. Ireland, 1892, p. 117; Liitkem. Desm. 

 Attersees, 1893, p. 538 ; West & G. S. West, Some X. Amer. Desm. 

 1896, p. 233, t. 12, f. 29 ; Obs. Conj. 1898, p. 52 ; Comcre, Desm. France, 



1901, p. 201, t. 16, f. 9 ; Ltitkem. Zellmembr. Desm, 1902, p. 361, t. 19, 

 f. 7 ; West & G. S. West, Alga-fl. Yorks. 1902, p. 110 ; Alg. N. Ireland, 



1902, p. 60 ; Alg. Ceylon, 1902, p. 194 ; G. S. West,. Brit. Freshw. Alg. 

 1904, p. 177, f. 69 C f Borge, Sao Paulo Alg. 1918, p. 74. 



Arthrodesmus ? cylindricum Ehr. Inf. 1838, p. 142. 

 Hyalotheca cylindricum Ehr. in Berlin Monatsb. 1840, p. 212. 

 Desmidium compressum Corda in Aim. de Carlsbad, 1840, p. 18. 

 Didymoprium GrevilUi Kivtz. Phyc. generalis, 1843, p. 166 ; Phyc. Germ. 



1845, p. 141 ; Ralfs, Brit. Desm. 1848, p. 57, t, 2 ; Kiitz. Spec. Alg. 



1849, p. 189; Breb. Liste Desm. 1856, p. 118: Arch, in Pritch. Inf. 



1861, p. 723; Pxabenh. Krypt.-fl. Sachs. 1863, p. 180; Reiiisch, Alg. 



Frank. 1867, p. 207 ; De Not. Desm. Ital. 1867, p. 27, t. 1, f. 3 ; Rabenh. 



Flor. Europ. Alg. 1868, p. 153 ; Delp. Spec. Desm. subalp. 1873, p. 52, 



t, 1, f. 20-28 ; Hauptfl. Zellm. u. Hullgallerte Desm. 1888, p. 16 and 50, 



t. 1, f. 39-60 (sep.); Hustedt, Desm. et Bacill. Tirol, 1911, p. 342; 



Kaiser, Alg. Traunst. u. Chiemgau, 1914, p. 154. 

 D. cylindricum Ralfs in Ann. Mag. Nat. Hist. v. 16, 1845, p. 10. t. 3, f. 4 ; 



Turn. Alg. E. India. 1893. p. 150. 



Desmidium Grcnllll De Bary, Conj. 1858, p. 76 r t. 4, f. 30-31. 

 D. (Didymoprium) cylindricum Nordst. Norges Desm. 1873. p. 49. 



Cells large, about 2-21 times broader than long, 

 constriction slight, sinus linear ; semicells very short, 

 pyramidate- truncate, basal angles acutely rounded, 

 lateral margins gently biundulate ; apex broad and 

 truncate : cells in vertical view elliptical with a rounded 

 mamilla-like protuberance at each pole ; chloroplasts 

 axile, one in each semicell, usually with four massive 

 radiating lobes, in each of which is a pyrenoid ; cells 

 united by their broad, flat apices to form twisting fila- 

 ments, with a thickened protruding rim between each pair 

 of cells ; filaments usually enclosed in a gelatinous sheath. 



Zygospores formed after the dissociation of the fila- 

 ment into individual cells ; large and smooth, globose 

 or sub globose, contained in one of the conjugating 

 cells, the other remaining attached. 



Length about 24 u ; greatest breadth 41-56 \L ; 

 breadth of isthmus 45-47 [JL ; breadth of apices 26-40 ;JL ; 

 thickness 25-38 u. ; diam. zvgosp. 26-40 u. [Much 



1 / o -L 



larger specimens sometimes occur, bub exact measure- 

 ments of such individuals were not available.] 



