146 YORKSHIRE NATURALISTS' UNION. 



723. Lyngbya Rivulariarum Gomont, 1893. 



Mid W. — Among the filaments of Rivularia hce/natites, on 

 wet rocks, Penyghent. 



724. Lyngbya versicolor (Wartm., 1861) Gomont, 



1893. 

 Mid W. — Among Schizothnx MiUleri Nag., on wet rocks, 

 Linn Gill. 



Sub-Family Oscillarioide^. 

 Genus PHOR.MIDIUM Kiitz., 1843. 



725. Phormidium molle (Kiitz., 1849) Gomont, 1893. 



[Syn. Anabcena mollis Kiitz., 1849]. 

 N.E. — Pilmoor, near Thirsk. 



Forma tenuior. Thickness, trichome 2 — 2 •4^1; long, artic. 

 2-2— 3'5 \>. 



S.W. — Bradford. This formed bright aeruginose coatings on 

 the roots and fronds of Lemna minor. It differs in no respect 

 from the type except in the somewhat narrower trichomes. 



726. Phormidium luridum (Kiitz., 1849) Gomont, 



1893. [Syn. Leptothrix lurida Kiitz., 1849; 

 HyplKBOthrix lurida Rabenh., 1865.] 

 S.W. — Frizinghall. Horton Park, Bradford. Heaton. 

 Thickness, filaments i"6 — 2 /x ; long, artic. 2 '5 — 4*2 /x. 

 Mid W. — Boston Spa. 

 N.E.— Stokesley. 



727. Phormidium purpurascens (Kutz., 1847) 

 Gomont. 1890. 



[Syn. Leptothrix purpurascens Kiitz., 1847]. 



Mid W. — Forming bright reddish-purple coriaceous patches, 

 some square feet in extent, on the face of dripping limestone 

 rocks, Linn Gill. The stratum has a smooth shining surface 

 and consists of densely intricate and tortuose minute filaments 

 (thickness, trichome i "5 — 2 \x). Also on dripping limestone 

 rocks, Cowside Beck, near Arncliffe. Ingleton. 



This species has not previously been recorded for the British 

 Isles. 



Trans. Y.N.U., 1899 (pub. July 1901). Bot. Series, Vol. 5. 



