252 NEMATOGEN A. 
ments beautifully granulated, extreme apex broadly rounded, or 
somewhat beaked, cell-contents homogenous or delicately 
granular. 
Sizz. 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 186]. 
Plate XCVII, fig 5. Portions of trichomes X 400. 
Oscillaria nigra. Vauch. Conf.192, ¢. 15, f. 4. 
Stratum more or less compact, somewhat membranaceous, 
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. diam. 
Rabh. Alg. Eur. i., 107. Kirch. Alg. Schl. 247. Harv. 
Man. 165. Eng. Fl. v., 376. Eng. Bot. t. 2527. 
Oscillatoria nigra, Hass. Alg. 255, t. 71, f.3. Hook. FI. 
Scot. 79. Jenn. Tunb. Wells 188. Mack. Hib. 239. Gray 
Arr. i, 281. 
Conferva fontinalis, Dillw. Conf. t. 64. Huds. Fl. Ang. 
592. Lightf. Fl. Scot. 976. With. Arr. iv., 128. 
In ditches and ponds. 
“Stratum extensive, blackish, with a shade of green, when dry blue- 
black, very rapid in its growth, and sending out long, vividly oscillating 
rays.”— Harvey. 
Plate XCVII. fig.6. Portions of trichomes x 400. 
Oscillaria nigro-viridis, Thwaites in Harv. Phye. 
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. Phyce. Britt. t. 251 4. Rabb. Alg. Eur. ii.. 292. 
In brackish ditches. August. 
Plate XCVIIJ. fig. 2. Trichomes of O. nigro-viridis X 400 diam. 
