The Freshwater Algae of Africa. 563 



Differt a typo cellulis majoribus, apicibus plus minus complanatis, 

 isthmo latiore; a vertice visis ellipticis vel triangulares, angulis 

 rotundatis. Cellulis aut singulis aut in filis brevibus dispositis, saepe 

 algis filamentosis adhaerentibus. 



Attention may be drawn to the similarity between these specimens 

 and Cosmarium minimum, W. & G. S. West (op. cit., iii, 1908, p. 66, 

 PL LXXI, figs. 1, 2), as well as C. inconspicuum, W. & G. S. West 

 (loc. cit., ii, 1905, p. 164, PI. LXI, figs. 1, 2). Both of these show 

 certain differences, but in view of the capacity of 8. pygmaeum to 

 exist in the non-filamentous condition, the possibility of some of these 

 minute Cosmaria being forms or varieties of this species should be 

 kept hr sight. Another form that bears some resemblance to the 

 specimens of 8. pygmaeum with triangular end-views is Staurastrum 

 coarctation, Breb., var. curtum, Nordstedt (Vid. Medd. Nat. Foren. i. 

 Kjobenhavn, 1869, p. 224, Fig. 50). 



(3) ZYGNEMAOEAE. 



Genus SPIROGYRA Link. 



1. ? Spirogyra maxima (Hass.), Wittrock, Bot. ISTotiser, 1882, p. 57; 

 Borge, Zygnemales, in Suesswasserfl. Deutschl., Oesterreichs u. d. 

 Schweiz, ix, 1913, p. 55, fig. 46. (Syn. : 8. orbicularis (Hass.), 

 Kuetz.) 



Samples 46, 47. 



Diam. fil., 150-170 /x. Many of the filaments were in process of 

 conjugation, but none had formed any zygospores. The characters of 

 the vegetative filaments, however, altogether agree with the above 

 species. 



2. Spirogyra juergensii, Kuetzing, Phycol. german., 1845, p. 222 ; 

 Borge, op. cit., p. 23, fig. 23; Petit, Spirog. d. env. d. Paris, 1880. 

 pp. 16, 17, PI. V, figs. 6, 7. 



Sample 32 (not very common). 



Diam. fil., 24-25 /x ; lat. zygosp., 30 \x ; long, zygosp., 54-60 f i. 



The specimens agree exactly in vegetative and reproductive characters 

 with the description in Petit (loc. cit.). The fructifying cells are very 

 slightly inflated to accommodate the zygospores. Some authorities 

 regard this species as a form of S. porticalis (Muell.), Cleve (Syn. : 8. 

 quinina (Kuetz.), Kirchn.), but it seems sufficiently distinct to warrant 

 a separate species. 



3. Spirogyra hassallii (Jenner), Petit, op. cit., p. 12, PI. II. figs. 6-8 ; 

 Borge, op. cit.. p. 19, fig. 11. 



39 



