Contributions to Our Knowledge of the Freshwater Algae of Africa. 35 
a and a\ the shape is somewhat variable, the angles tending to round ofl: in 
some specimens. In some cases there was a slight thickening of the 
membrane at the apex, and as a rare feature the latter appeared very faintly 
retuse. The membrane was mostly, but seemingly not always, punctate. 
The specimens differ both from the type and from var. africanum, W. & Gr. S. 
West, in the very narrow apex, but even in this respect there was a certain 
amount of variation. 
The form here described is somewhat similar to that recorded from the 
Cape Peninsula (Fritsch, loc. cit., p. 555, fig. 28, c), but has, on the whole, 
a narrower apex. It also shows some resemblance to forms of C. granatum^ 
Breb., described by Borge (" Subfoss. soetvattensalg. fran Gotland," ' Bot. 
Notiser,' 1892, p. 56, and especially fig. 6). 
12. Cosmarimn laeve, Rabenhorst, Fl. Europ. Alg., iii, 1868, p. 161 ; 
W. & a. S. West, loc. cit., p. 99, PI. LXXIII, figs. 8-19. 
Forma typica. Long, cell., 22-36 ^ ; lat. cell., 16-24 /x; lat. isthm., 
4-5-6 /x; crass., 12 fx; lat. zygosp., 16 Membrana saepe laevis. (Fig. 11, 
F, a, b.) 
Samples 86, 327 (with zygospores), 345. 
Previously recorded from Little Namaqualand (Gr. S. West). 
Forma minor ad var. octangulareni (Wille), W. & Gr. S. West accedens. 
Long, cell., 16 /x ; lat. cell., 15 /x ; lat. isthm., 3 /x. 
Sample 158 (very rare). 
Forma rotu7idata. Apicibus non retusis. Long, cell., 30-31 /x; lat. cell., 
18-19 /X ; lat. isthm., 5-6 /x. (Fig. 11, F.) 
Sample 327 (rather rare). 
Forma acuminata. Lateribus valde convergentibus, apicibus subrotun- 
datis non retusis ; semicellulis a latere visis lateribus plus rotundatis. Long. 
celL, 30 /X ; lat. cell., 22 /x; lat. isthm., 6 /x ; crass., 14 /x. (Fig. 11, D.) 
Sample 327 (rare). 
It is manifest that C. laeve is very variable in South Africa, since other 
forms have already been recorded from the Cape (Fritsch, 1918, p. 555). 
The specimens illustrated in Fig. 11, D, F, and F, were all drawn from the 
material in sample 327, but they only represent the outstanding forms, and 
numberless transitions between them were encountered. The typical form 
(Fig. 11, F, a) has retuse apices and smooth, rounded sides, the membrane 
in the present material being never more than obscurely punctate and in 
many cases seemingly quite smooth (c/. Fritsch, loc. cit., p. 555). According 
to Messrs. West's monograph, " the slight retuseness in the middle of the apex 
is characteristic of all forms of the species," but it appears doubtful whether 
this statement really applies. Messrs. West (" Freshwater Chlorophyc," in 
J. Schmidt, ' Fl. Koh Chang, Bot. Tidsskrift,' xxiv, 1901, Tab. II, fig. 14) 
