Contributions to Our 'Knowledge of the Freshivater Algae of Africa. 63 
10. Oscillatoria subtilissima, Kuetzing, Tab. Phycol., i, 1845, p. 27, 
Tab. XXXYIII, fig. 8; Forti, op. cit., p. 171. 
Sample 335 (rather common). 
This form occurred on the surface of the investment of Nostoc sp. The 
trichomes (diam., 1*5 fx) in part formed almost parallel bundles, in part 
were rolled up in a circinate manner. They showed a faint constriction at 
the dissepiments, which were fairly conspicuous. It has been suggested 
tbat this species may be a form of Lyngbya rivtilariorum, Gom. (cf Ann. S. 
Afr. Mus., ix, 1918, p. 574), and the mode of occurrence of the present 
material is not in disagreement with this. 
Genus SPIEULINA Turpin. 
1. Spirulina major, Kuetzing, Phycol. generalis, 1843, p. 183 ; Gomont, 
op. cit., p. 251, PI. VII, fig. 29. 
Sample 326 (rather rare). 
Previously recorded from Little Namaqualand (G. S. West), the Cape 
and Orange Free State (Fritsch). 
Genus PHORMIDIUM Kuetzing. 
1. Phormidium fragile, Gomont, op. cit., p. 163, PI. lY, figs. 13-15. 
Sample 324 (bearing numerous epiphytes : Oscillatoria splendida, Lyngbya 
aestuarii, Chroococcus turgidus. Microcystis spp., Microcoleus chthonoplastes, 
Anabaena torulosa). 
Previously recorded from Holle River (G. S. West). 
2. Phormidium valderianum, Gomont, op. cit., p. 167, PI. IV, fig. 20. 
Sample 159 (rather common). 
Previously recorded from Cape Town (Fritsch). 
3. Phormidium lammosum, Gomont, op. cit., p. 167, PI. IV, figs. 21, 22. 
Sample 81. 
Previously recorded from Little Namaqualand and Holle River (G. S. 
West). 
4. Phormidium tenue, Gomont, op. cit., p. 169, PI. IV, figs. 23-25. 
Samples 71, 85. 
Previously recorded from Holle River and Little Namaqualand (G. S. 
West). 
5. Phormidium inundatum, Kuetzing, Spec. Alg., 1849, p. 251 ; Gomont, 
€p. cit, p. 172, PI. IV, figs. 31, 32. 
Sample 68. 
Diam. fil., 4-6 fi. 
