The Freshwater Algae of Africa. 



515 



(e) CFLOTRICHALES. 



(1) ULOTRICHACEAE. 



Genus ULOTHRIX Kuetzing. 



1. TJlothrix variabilis, Kuetzing, Spec. Algar., 1849, p. 346 ; Heering, 

 Ulotrichales, Microsporales, Oedogoniales, in A. Pascher, Suess- 

 wasserfl. Deutschlands, Oesterreichs, u. d. Schweiz, vi, 1914, p. 32, 

 fig. 27. 



Samples 3 (rare), 8, 9, 10, 37. 



$3 



m 



\ m \ 



Fig. 10. — Ulothrix oscillarina, Kuetz. A-C. Filaments showing formation 

 of akinetes. D. Filament showing splitting. All figures x 800. 



2. Ulothrix subtilissima, Rabenhorst, Krypt. Flor. v. Sachs., etc., I, 

 1863, p. 263 ; Heering, op. cit, p. 31, fig. 26. 



Samples 19, 50. 



The form in sample 50 had thick gelatinous walls. 



3. Ulothrix oscillarina, Kuetzing, op. cit., p. 346 ; Heering, op. cit., 

 p. 32 (fig. 10). 



Samples 56 and 57 (common). 



I believe I am right in referring the material in these samples to 

 this little-known species. The filaments were rather variable in width, 

 many of them being 10-11 fx, but others as narrow as 7 or 8 /x. The 

 cells in many of the filaments were very flat (one-third to half as long 

 as broad) (cf. Fig. 10, A), whilst in others they were much longer 



36 



