58 BRITISH nESMTPIAOEJE. 



Archer, Observations on Cylindrocystis, 1S66, p. 206. 

 Gay, Monogr. loc. Conj. 1884, p. ::!. 

 Cooke, Brit, Desm. 1880, p. 46. 

 De Toni, Syll. Alg. 1889, p. 815. 



Cells cylindrical, about twice longer than their dia- 

 meter, often embedded in mucilage, unconstricted or 

 with a slight median constriction, apices generally 

 rounded ; with one axile, substellate chloroplast in 

 each semicell ; pyrenoids large, one in the centre of 

 each chloroplast. 



The principal character of this genus is the presence in each 

 semicell of a somewhat stellate chloroplast. In the centre of 

 the semicell is a large pyrenoid, and radiating from it in every 

 direction are processes and prolongations of the cliloroplnst, 

 which often flatten themselves against the inner surface of the 

 cell-wall. During conjugation the cell-walls of the game- 

 tangia become confluent round the zygospore in some species, 

 but not in others. 



A. Cells unconstricted. 



1. Cylindrocystis Brebissonii Menegh. 

 (PL IV, figs. 23-32 ; PI. V, fig. 10.) 



Cylindrocystis Brebissonii Menegh. 1838 ; Monogr. Nostoch. 1842, p. 89, 

 t. 12, f. 13 ; Hass. Brit. Freshw. Alg. 1845, p. 361, t. 92, f. 17 ; De Bary, 

 Conj. 1858, p. 35, 46, 74, t. 7, f. E 1-22 ; West, Alg. W. Ireland, 1892, 

 p. 131; Roy & Biss. Scott. Desm. 1894, p. 62 (sep.) ; West & G. S. 

 West, Alga-fl. Yorks. 1900, p. 43 ; Alg. N. Ireland, 1902, p. 20. 



Palmoglcea Brebissonii Kiitz. Tab. phycolog. I, 1847, p. 19, t. 24, f. 4 ; 

 Spec. Alg. 1849, p. 229. 



Penium Brebissonii Ralfs, Brit. Desm. 1848, p. 153, t. 25, f . 6 ? ; Rabenh. 

 Flor. Europ. Alg. Ill, 1868, p. 120; Delp. Desm. subalp. p. 88, t. 14, 

 f. 28-36 ; Kirclm. Alg. Schles. 1878, p. 136 ; Wolle, Desm. U.S. 1884, 

 p. 36, t. 5, f . 7-8 ; Cooke, Brit, Desm. 1886, p. 43, t. 17, f. 3 ; West, Alg. 

 N. Yorks. 1889, t. 291, f . 3. 



Cells cylindrical, unconstricted, about 2-3 times 

 longer than their diameter, apices rounded ; chloro- 

 plasts usually with few large radiating prolongations 

 and often difficult of observation. 



Zygospore quadrate at first, and afterwards spherical 

 or subspherical or subquadrate. 



Length 43-55 yu ; breadth 15-18 ^u; diam. zygosp. 

 30-48-5 KJ 



