BY G. I. PLAYFAIR. 533 



Var. AMPLUM(West) mihi. (PI. Ivi., f.l3c). 



Lat. fil. 18-20; lat. trich. 4; cell. veg. alt. 12-20 /x. 

 Syn., Scy. amplum West, Frw. Alg. W. Ind., p. 270, PI. xvi., 

 f.14-16. 



Var. AMBiGUUM(Kutz.) mihi. (PI. Ivi., f.lSc?). 



Lat. fil. 18-20; lat. max. trich. 4; cell. veg. alt. 12-20 i^. 



Syn., Scy. ambiguum Kiitz., Fischerella ambigtia Gomont. 



These forms, besides being noted separately, wei'e all found 

 succeeding one another in the same filament within ^mm., as 

 figured. 



Genus Calothrix Ag. 

 ('?)CaLOTHRIX CONVERVICOLA(Roth) Ag. (Pl.lvi., f.14-16). 

 Diam. fil. 13-18; diam. trich. 12-13; cell. alt. 3-6; hormog. alt. 

 12-16/x. 



The characters are nearest to C. con/ervicola, but that is a salt- 

 water form. 



Genus Oscillatoria Vaucher. 

 O. NiGROViiUDis Thwaites, forma crassiok, n.f. 



Lat. trich. 12-15; alt. cell. 2-8 /x. 



Very common in the filter-samples. The margin, generally 

 crenulate, is occasionally quite smooth. The name is rather mis- 

 leading (if my identification is correct, cf. Askenasy in Bailey's 

 Bot. Bull, xi., p.50); the colour varies a good deal. The tints 

 observed in the trichomes of fresh specimens were grey-blue, dull 

 purple-blue, pale blue-green, dull green, the last predominating. 

 It is curious to find this species in the Water-supply, and in 

 various bodies of freshwater round Sydney, as it is generally 

 marine; and I have myself found it in saltwater swamps at New- 

 ington, and in the plankton of the Parramatta River (marine) 

 Trichomes from the latter were 14 ft in diameter, cells 3 /x alt. 

 and strong green in colour, 



Var. AUSTRALis, n.var. (Pl.lvi., f.17,18). 



Latitudine duplo major. 



I^t. trich. 25-27; alt. cell. 4-8 /ut. 



