Tlir Freshwater Algae of Africa. 523 



the threads were almost uniformly thickened all round (Fig. 14, c), but 

 in most cases the transverse septa were especially strongly thickened, 

 assuming a biconcave form (Fig. 14, b) ; sometimes a faint stratifica- 

 tion of the thickening could be recognised. In others of the filaments 

 the longitudinal walls had undergone rupture at many points, a new 

 membrane having appeared around the cell-contents and elongation 

 having taken place, with or without division (Fig. 14, a). The original 

 thickened biconcave septa, with the adhering strips of the longitudinal 

 walls, look very much like H -pieces and led me at first to interpret 

 the material as a species of Microspora. The tapering ends of these 

 strips often stood off from the surface of the filaments and gave them a 

 ragged appeai'ance (Fig. 14, a). The cells were in part very short, 

 sometimes half as long as broad. The character of the chloroplast, 

 where it could be distinctly seen, agreed with that of the vegetative 

 filaments of this species (cf. Fig. 14, c). 



In 1895, Schmidle (Weitere Beitr. z. Algenfl. d. Rhehiebene u. d. 

 Schwarzwaldes, Hedwigia, xxxiv, 1895, p. 69, figs. 4-5) described a 

 form under the name of Microspora lauterborni, which bears a consider- 

 able resemblance to the stages just described ; the habitat is also some- 

 what similar. The principal difference lies in the fact that the 

 filaments in Schmidle's species are often spiral in their course and that 

 his figures show distinct H-shaped ends to the threads. Schmidle does 

 not describe or figure the cell-contents, so that his reference of this 

 species to Microspora must be regarded as somewhat uncertain. It is 

 not impossible that it is a stage similar to that above described, 

 although whether it belongs to our species or to another is difficult -to 

 settle. 



(5) MICROSPORACEAE. 



Genus MICROSPORA Thuret. 



1. Microspore pachydermia (Wille), Lagerheim, Zur Entwickel. 

 einig. Confervaceen, Ber. Deutsch, Bot. Ges., v, 1887, p. 415. (Syn. : 

 Conferva pachydermia, Wille). 



Samples 11, 12, 13. 



Diam. til., 9-11 /x. The filaments were in part provided with a 

 brown incrustation of iron compounds, which is a character of the 

 nearly allied M. rufescens (Kuetz.), Lagerh. ; in other respects, how- 

 ever, they approached more closely to M. pachydermia . 



