The Freshwater Algae of Africa. 573 



Genus PHORMIDIUM Kuetzino. 



1. Phormidium valderianum, Gomont, op. cit., p. 167. PI. IV, 

 tig. 20. 



Sample 15. 



2. Phormidium subfuscum, Kuetzing, op. cit., p. 195; Gomont, op. 

 cit, p. 182, PI. V, figs. 17-20. 



Samples 41,43. 



Diam. trich., 9-10 fi. The apex of the trichomes Avas rather variable, 

 being either rounded and without a ealyptra or, more commonly, with 

 a typical conical or hemispherical ealyptra. In a considerable number 

 of cases the conical ealyptra was inequilateral. The degree of attenua- 

 tion of the apex also varied very considerablv. 



3. Phormidium autumndUe, Gromont, op. cit., p. 187, PI. V, figs. 23, 24. 

 (Syn. : P. uncinatum, Gtom.) 



Sample 27. 



Genus LYNGBYA C. Agardh. 



1. Lyngbya major, Menegh. ; Gomont, op. cit., p. 144, PI. Ill, 

 fig. 15. 



Sample 52. 

 Diam. trich.. 12-16 /> 



Previously recorded by Wille from South Africa; by G. S. West 

 from Little Namaqualand. 



2. Lyngbya aerugineo-coerulea, Gomont. op. cit., p. 146, PI. IV, 

 figs. 1-3. 



Samples 37, 41. 

 Diam. trich., 6 jj.. 



3. Lyngbya rivulariarum, Gomont, op. cit., p. 148. 



Forma paullo latior, apice curvato et interdum leviter attenuato. 

 Diam. fil., usque 1 \x. (Fig. 35.) 



Sample 30 (in the mucilage of Rivularia nutans). 



I have not seen a figure of Lt/iigbi/a rivulariarum, hut I have little 

 doubt that this form is closely allied to it. The sheath was very thin 

 and closely fitting ( Fig. 35, //), and but rarely obvious. The cells 

 were non-granular, had very hyaline septa, and were several times 

 longer than broad. Constriction between the cells was, in general, 

 not at all well-marked ; in fact, in the ordinary filaments, it was often 

 extremely difficult to recognise the limits of the individual cells. In 

 the case of short pieces of thread (hormogonia?), however, the con- 



