The Freshwater Algae of Africa. 501 



rapidity. The successive membranes of the cell are always plainly 

 visible, and enable one to estimate the number of processes of inno- 

 vation that have taken place. It is noticeable that the successive 

 membranes fit more or less closely around one another at their 

 ruptured ends (cf. especially Fig. 4, a), the wide apertures charac- 

 teristic of E. ramosa not being encountered in this species. 



Sooner or later, however, this process of l'ejuvenescence ceases and 

 division of the protoplast ensues. With the exception of those cases, 

 to be subsequently described as probable stages in reproduction, I 

 have never observed division into more than two parts in this species. 

 The plane of division is oblique (Fig. 4, b), as in E. ramosa. One of 

 the products appears ahvays to shift up to the rather narrow opening 

 of the mother-cell, whilst the other remains near its base. This seems 

 to be a constant feature of this species, although the basal cell may 

 not uncommonly be subsequently carried up to the opening of the 

 mother-cell by the process of rejuvenescence above described (Fig. 4, a 

 and/) ; in fact (as in Fig. 4, g), it may sometimes ultimately overtop 

 the sister-cell, which took up a position at the aperture. As a result 

 of this method of division, and of the behaviour of the products, the 

 colonies of E. simplex are far less abuudantly branched than those of 

 E. ramosa. 



The terminal cells of the colonies in this species were not 

 uncommonly found to have divided into a large number of small cells 

 (long. 18-21 ix, lat. 6-7-5 n) (cf. Fig. 4, d). In several, but not in 

 all cases, these cells appeared to be naked. As in E. ramosa, there is 

 a probability that the production of these small cells marks a stage in 

 the reproduction of the species. 



The cells of the ordinary individuals are in general very much elon- 

 gated, being not uncommonly six times as long as broad, The ends 

 are rounded, or very frequently more or less markedly pointed. The 

 lower ends of the cells, where they are surrounded by the attaching 

 mucilage, are always distinctly attenuated. The cell -contents were 

 very granular and difficult to decipher. Staining witii iodine seemed 

 to show a number of pyrenoids (4-6) in each cell, but I am not sure of 

 the number. Some of the small (reproductive?) cells appeai'ed to 



Pig. 4. — Ecballocystis simplex, n. sp. a. Colony showing rejuvenescence 

 and branching ; the mucilage-pads by means of which attachment is 

 effected are shown, b. Initial cell which has undergone two processes 

 of innovation and the protoplast of which is now undergoing oblique 

 division, c. A cell which has undergone repeated rejuvenescence and 

 has recently divided, one of the products of division having shifted up 

 to the aperture of the mother-cell, whilst the other has remained 

 within the latter, d. Formation of numerous division-products (re- 

 productive cells?), e, /j and ;/. Typical instances of branched colonies, 

 also showing good examples of innovation. All figures x 600. 



