198 SYNOPSIS OF BRITISH SEAWEEDS. 



curved and twining together ; the Btriae very dense, and the 



mass of endochrome divided at uncertain intervals into por- 

 tions, which probably break off eventually and become new 

 filaments. 



373. subsalsa {The marine Oscillatoria) , Ag. Hook. Brit. Fl. 

 v. 2. p. 376. 



Hab. ? 



A species of Agardh's, cited in the ' British Flora,' which 

 is at present unknown to me. 



371. spiralis {The spiral Oscillatoria) ; stratum membrana- 

 ceous or coriaceous, aeruginous or blackish-green, without 

 much lubricity ; filaments slender, spirally twisted, densely 

 interwoven, radiating in all directions, Carm. Alg. Appin. 

 ined. (Atlas, PI. LXXIX. Fig. 373.) 

 Spirillum rupestre, Hass. 

 Hab. On rocks by the seaside, above and between tide-marks. 



Specimens from the south of England are of a much 

 brighter colour, with the stratum thinner than in the ori- 

 ginal Scotch specimens, but the microscopic character is 

 very similar. Whether the 0. subsalsa of Agardh be dif- 

 ferent, I am unable to say. 



375. nigro-viridis ( The dark-green Oscillatoria) ; stratum of a 

 very dark olive-green colour ; filaments delicate, pale-green, 

 rigid, with obtuse, curved apices ; striae inconspicuous, dis- 

 tant about half a diameter of the filament ; endochrome very 

 slightly granulose, Thwaites, Harv. Phyc. Brit. pi. 251, A. 

 (Atlas, PL LXXIX. Fig. 375.) 



Hab. In a brackish ditch at Shirehampton, near Bristol. 



Mr. Thwaites, in communicating this plant to me, ob- 

 serves, "This species, which I have met with only once, 

 bears some resemblance, as has been remarked to me by 

 the Eev. M. J. Berkeley, to Oscillaria uncinata of Kiitz- 

 ing, but the latter is a smaller species than ours, and has 

 the stria? of its filaments more distinctly marked." 



376. subuliformis {The awl-shaped Oscillatoria)-, stratum of 

 an intense aeruginous-green colour ; filaments bright-green, 

 subuliform ; striae inconspicuous, distant from one-half to 

 three-quarters of a diameter of the filament ; endochrome 

 not evidently granulose, Thivaites, Harv. Phyc. Brit. pi. 

 251, B. (Atlas, PL LXXIX. Fig. 376.) 



Hab. In brackish ditches, at Shirehampton, near Bristol, during 

 the summer and autumn. Not uncommon. 

 Of this plant the discoverer remarks, " This beautiful 



