The Freshwater Algae of Africa. 571 



either had homogeneous pale blue-green contents or some or all of the 

 cells were provided with gas-vacuoles. The cells were not very densely 

 arranged, being generally separated by more than their own diameter 

 from one another. 



The different species of Microcystis are so imperfectly known that it 

 is very difficult to decide on the position of this form ; it comes near 

 to those species which have free-floating, more or less spherical 

 colonies, e. g. M. protogenita (Bias), Rabenh., M. olivacea, Kuetz.,etc, 

 in which, however, the cells are generally much more densely crowded. 

 In the relatively remote spacing of the cells our form approaches the 

 smaller species of Aphanocapsa (e.g. A. elachista,'W. & G. S. West), 

 which are altogether very hard to separate generieally from Micro- 

 cystis. I am not, however, aware that a development of gas-yacuoles 

 has been recorded in the former genus. 



There is also a resemblance to Aphanocapsa grevillei, Rabenh., var. 

 microgranula, W. West (Algae W. Ireland, Jouru. Linn. Soc, Bot., xxix. 

 1891, p. 199, PL XVIII, fig. 9), which might perhaps be better 

 referred to the genus Microcystis. 



Genus GOMPHOSPHAERIA Kuetzing. 



1. Gomphosphaeria lacustvis, Chodat, Bull. d. L'Herbier Boissier, 

 vi, 1898, p. 180, fig. 1 ; Forti, op. cit., p. 99. 

 Sample 39 (rare). 



G-enus MERISMOPEDIA Meten. 



1. Merismopedia glauca (Ehrenb.), Naegeli, Gatt. einzell. Alg., 

 1849, p. 55, PI. I, D, fig. 1 ; Forti, op. cit.. p. 105. . 



Sample 25 (very rare). 



Previously recorded by Wille from South Africa ; by G. S. West 

 from Little Namaqualand. 



(h) CHAMAESIPHOXALES. 

 (1) CHAMAESIPHONACEA K. 



Genus CHAIMA LSI PHON Bkaun & Gbunow. 



1. Chamaesiphon incrustans, Grim. ; Rabenhorst, Fl. europ. Alg., 

 ii, 1865, p. 149: Forti, op. cit, p. L36. 

 Sample 29 (on Oedogonium boreale). 



