SPIRULINA. 229 



ral feel in extent, firm, coriaceous, of a glossy black colour, void of lubri- 

 city. Filaments about half a line in length, twisted like a cork-screw, 

 radiating in all directions." Carm. 



4. O. nigro-viridis, Thw. ; stratum of a very dark olive- 

 green colour ; filaments delicate pale green, rigid, with ob- 

 tuse, curved apices ; striae inconspicuous, distant about half 

 the diameter of the filament ; endochrome very slightly gra- 

 nulose. Tlnv. in Haw. Phyc. Brit. t. ccli. A. 



In a brackish ditch at Shirehampton, Bristol, Mr. Thwaites. — Stratum 

 thick, dark olive-green, almost black, growing on mud and subsequently 

 floating. Filaments pale dull green, with distinctly curved apices. 



5. O. subiiliformis, Thw. ; stratum of an intense aerugi- 

 nous green colour; filaments bright green, subuliform ; striae 

 inconspicuous, distant from one-half to three-quarters of a 

 diameter of the filament ; endochrome not evidently granu- 

 lose. Thic. in Harv. Phyc. Brit. t. ccli. B. 



With the preceding. Summer and autumn. Mr. Thwaites. — Stratum 

 thin, appearing black in the water, but when taken out, of a beautiful deep 

 blue-green colour. 



o' 



6. O. insignis, Thw. ; stratum of a dark brown, almost 

 black colour ; filaments brown, of considerable diauieter, 

 their apices obtuse, slightly oblique and ciliated ; striae con- 

 spicuous, very close ; endochrome distinctly granulose. Thw. 

 in Harv. Phyc. Brit. t. ccli. C. 



With the preceding. November. Mr. Thwaites — Stratum thin, spread- 

 ing over decaying vegetable matter. Filaments very large and rather 

 brittle. 



VIT. Spirulina. Turp. [Plate 27, C] 



Filaments lying in a mucous layer, rigid, simple, spirally 

 twisted, vividly oscillating. Tube continuous ; endochrome 

 green, more or less distinctly annulated. — Name, a diminu- 

 tive of spira, a twist or curl. 



1. S. ienuissima, Kiitz. ; stratum very lubricous, oerugi- 

 nous, subradiant ; filaments densely spiral, very slender, 

 parallel, flexuous. Harv. Phyc. Brit. t. cv. C. 



On decaying Algae, in a brackish pool, near Menai Bridge ; and on sticks 

 in brackish pools, at Penman Pool, Dolgelly, Mr. Ralfs. Aberdeen, Dr. 

 Dickie. — Forms a gelatinous pellicle of a rich green colour. Filaments 

 very slender, vividly oscillating. 



