The Freshwater Algae of Africa. 



517 



eadem forma, sed semper cum margiuibus in pi-ocessibus plus minus 

 elongatis productis, ita ut in Chaetoplioraceis ; pyrenoide singulo vel 

 pluribus. Nucleo centrali. Propagatio ? 

 Sample 4. 





Pig. 11. — Ulothrix gelatinosa, n. sp. a. Middle-aged, h young, and c 

 mature filaments ; A, e, and g filaments in various stages of develop- 

 ment ; /, single cell of ii mature filament showing the character of the 

 ohloroplast, etc. In Fig. b, the type of chloroplast, typical of the young 

 filament, is shown ; in Pigs, a, c, and / that typical of the mature con- 

 dition ; whilst Figs, d, e, and g represent intermediate conditions. The 

 central nucleus is shown in many of the cells ; both nucleus and pyre- 

 noids are seen in Fig./. All figures x 600. 



This species is characterised by the very marked gelatinisation of 

 the walls in the older filaments, as well as by the shape of the chloro- 

 plast. The latter is at first a curved median girdle (like that of many 

 other species of the genus), occupying only a small part of the length 

 of the cell, and extending for rather more than half way round the 



