oscillatoriacejE. 289 



in brackish ditches, at Shirehanipton, near Bristol. I 

 cannot find them in Kiitzing's ' Species Algarum/ and 

 I have no more recent work at hand to which I can refer. 

 I am not myself acquainted with them. 



Genus CXX. SPIRULINA. 



Fronds simple, rigid, spirally twisted, vividly oscillating 

 threads, developed in a thin gelatinous layer ; tube continu- 

 ous ; endochrome green, more or less distinctly annulated. 

 — SpiErLiNA, from the Latin spira, a twist. 



Spirulina tenuissima. The very slender Spirulina. 



" Stratum very lubricous, aeruginous, sub-radiant ; fila- 

 ments densely spiral, very slender, parallel, flexuous." — 

 Phyc. Brit. 



This species grows on decaying sea-weeds ; or wood in 

 brackish water. 



Genus CXXI. TOLYPOTHEIX. 



" Filaments of nearly equal diameter, tufted, tenacious ; 

 branches free, continuous, with main filaments annulated at 

 the base; cells indistinct, rarely moniliform." — Toltpo- 

 theix, from the Greek tolupe, a clew, or ball wound up, and 

 thrix, hair. 



I have taken the description of this genus from Dr. 

 Gray's Handbook. The only British species that is 

 marine was formerly Calothrix fasciculata. 



Tolypothrix fasciculata. The fascicled Toly- 

 pothrix. 



Threads straight, awl-shaped, tapered, at first simple, 



u 



