The Freshwater Algae of Africa. 



513 



of the colonies were quite free. The spherical cells are connected 

 together by processes which are broader and shorter than the warts 

 which occur on the free surface of the cells (Fig. 9, a c). These 

 warts were emarginate-truncate, as in the specimens recorded by 

 Messrs. \Y. & G. S. West; but they were certainly fewer (the 

 largest number observed on a single cell being 16) and further apart 

 (>/'. Fig. 9). In many cases they appear to widen out slightly from 

 the base. The length of these warts varies considerably in different 

 specimens, the dimensions given above being the maximum ones. 



Fig. 9. — Coelastrum morus, \\ . and G. S. West, forma capensis, nov. form. 

 a, c, d. Various forms of the colonies ; in d the colony is still enclosed 

 within the membrane of the mother-cell. b. Single cell, showing warts 

 and the broad process for attachment to neighbouring cells ; the con- 

 tents arc undergoing division. b l . Cell in optical section, showing the 

 thick membrane. All figures x 750. 



The cells were grouped in very various ways, which is probably 

 a result of the mode of life. Apart from typical Coelastrum-gvou^iiigs 

 (Fig. 9, d), irregular colonies were frequent (Fig. 9, c). Not un- 

 commonly the cells were found in two superposed groups of four 

 (Fig. 9, a), the four cells of each tier being separated in the middle 

 by a quadrilateral space, so that a surface-view of such a colonv 

 appeared much like a Crucigenia. The details of the cell-contents 

 were not very clear, but the cells appeared to have a single pyrenoid. 

 The membrane is strongly thickened (Fig. 9, &'). 



Genus DICTYOSPHAERIUM Nae.ieli. 



1. Dictyosphaerium ehrenbergianum, Naegeli, Gatt. einzell. Algeu., 

 1849, p. 74, Tab. II, E. 

 Sample 14 (very rare). 



