The Freshwater Algae of A frica. 597 



2. Nitzschia apiculata (Greg.), Grun. ; Van Heurck, op. eit., p. 173, 

 PL LVIII, figs. 26, 27. 

 Sample 34a. 



Long., 36 ji. ; hit., 6 ft. 



Section DUBIAE Grunow. 



1 Nitzschia stagnorum, Rabenhorst ; Van Heurck, op. cit., PL LIX, 

 Eg. 24. 



.Sample 32. 



Long., 45 (x ; lat., 6-8 /x. 



Recorded from the Halle River, Calvinia Division, by G. S. West. 



Section SIGMOIDEAE Grunow. 



1. Nitzschia sianwidea (Ehrenb.), W. Smith, op. cit., i., p. oH, 

 PL XIII, fig. 104; Van Heurck, op. cit., p. 178, PL LXIII, figs. 5-7. 

 Samples 4.5, 6, 25, 32. 



Section SIGMATAE Grunow. 



1. Nitzschia sigma (Kuetz.), W. Smith, op. cit, i, p. 39, PL XIII, 

 fig. 108 ; Van Heurck, op. cit., p. 179, PL LXV, figs. 7, 8. 



Samples 4, 52, 54. 



Var. subcapitata, Rabenh. (N. clausii, Hantzseh ; Van Heurck, op. 

 cit., PL LXVI, fig. 10). (Fig. 41,/.) 



Samples 4, 6. 



Long., 54-60 fx ; lat., 4-5 ll. 



The specimens were often more markedly curved than shown in 

 fig- 41,/. 



Var. sigmatella, Grun. ; Van Heurck, op. cit., p. 179, PL LXVI, 

 figs. 6, 7. (Fig. 41, a.) 



Sample 6. 



Long., 96-150 p ; lat., 4-5-5 /x. 



? Var. rigid ida, Grun.; Van Heurck, op. cit., p. 179, PL LXVI, 

 fig. 8. (Fig. 41, &.) 



Sample 5. 



A form with slightly capitate ends, rather wide, and with well- 

 marked carinal dots. 



Long., 80-86 /x; striae very fine. 



Section LANCEOLATAE Grunow. 



1. Nitzschia subtil is, Grun. ; Van Heurck, op. cit., p. 183, PL 

 LXVIII, figs. 7, 8. 



