252 NEMATOGENJE. 



ments beautifully granulated, extreme apex broadly rounded, or 

 somewhat beaked, cell-contents homogenous or delicately 

 granular. 



SIZE. Threads '0076--01 mm. 



Kutz. Tab. Phyc. i., t. 42, f. 4. Rabh. Alg. Eur. ii., 107. 



On wet rocks, walls, or overrunning mosses. 



The variety " subsalsa," bearded at the apex, was found on Greenwich 

 Pier in 1861. 



Plate XCril. fig 5. Portions of trichomes X 400. 



Oscillaria nigra. Vauch. Cow/. 192, t. 15, f. 4. 



Stratum more or less compact, somewhat membranaceons, 

 often floating, steel-blue, or dark olive nearly black, with radii 

 more or less elongated, of the same colour. Trichomes straight 

 or slightly flexuous, obtusely rounded at the apex, or attenuated, 

 and sometimes bearded ; joints equal in length to their diameter 

 (after division one half or one third as long) ; dissepiments very 

 distinctly granulated, apiculus often straight, somewhat rostel- 

 late and bearded, rarely slightly curved ; cell-contents pale olive, 

 finely granular. 



SIZE. Threads *009-'01 mm. diaun. 



Rabh. Alg. Eur. i., 107. Kirch. Alg. Schl. 247. Harv. 

 Man. 165. Eng. Fl. v., 376. Eng. Bot. t. 2527. 



Oscillatoria rdgra, Hass. Alg. 255, t. 71, f. 3. Hook. Fl. 

 Scot. 79. Jenn. Tunb. Wells 188. Mack. Hib. 239. Gray 

 Arr. i., 281. 



Conferva fontinalis, Ih'llw. Conf. t. 64. Huds. Fl. Aug. 

 592. Lighlf. Fl. Scot. 976. With. Arr. iv., 1^8. 



In ditches and ponds. 



" Stratum extensive, blackish, with a shade of green, when dry bine- 

 black, very rapid in its growth, and sending out long, vividly oscillating 

 rays.'' Harvey. 



Plate XCVII.fg. 6. Portions of trichomes X 400. 



Oscillaria nigro-viridis. Thwaites in Harv. Phyc. 



Stratum thin, of a dark olive green, almost black, growing 

 upon the mud, and subsequently floating in large masses. 

 Trichomes pale dull green, with obtuse, distinctly curved, 

 scarcely attenuated apices ; joints indistinct, about half as long 

 as broad, cell-contents slightly granulose. 



SIZE. Trichomes '012 mm. diam. 



Harv. Phyc. Britt. t. 251 A. Rabh. Alg. Eur. ii.. 292. 



In brackish ditches. August. 

 Plate XCVII1. jig. 2. Trichomes of O. nigro-viridis X 400 diam. 



