Contributions to Our Knowledge of the Freshwater Algae of Africa. 17 
Fig. 6). The lower part of the thallus of a mature specimen is a broad 
structure passing over gradually, on the one hand into the fan-shaped 
attaching organ (Fig. 5), and on the other hand into the numerous branches 
that arise just above the base (Figs. 4, A, and 5), The organ of attachment 
is composed of closely apposed, more or less radiating rows of rather narrow 
and elongated cells (Fig. 5). The cells in the thallus proper are never 
markedly elongated, but apart from that vary much in shape. In part they 
are approximately isodiametric, as seen from the surface, in part somewhat 
drawn out in the transverse or longitudinal direction (Fig. 4, E-G). In 
optical section, at the edge of the thallus, they either appear elongated at 
Fig. 5. — Enteromorpha hasiramosa, F. E. Fritsch, n. sp. Attaching base and 
lower portion of a mature thallus. x 40. 
right angles to the surface or somewhat flattened. As shown in Fig. 4, E 
and F, the shape of the cells may vary appreciably, even in small parts of a 
thallus. In the vast majority of cases the cells are arranged in very obvious 
longitudinal rows (Fig. 4, B and E), which were sometimes observed to have 
a slight spiral trend. In the broadest filaments, however, this regular 
disposition, though still recognisable, may become somewhat obscured 
(Fig. 4, F). The outer wall of the cells is markedly thickened — more so than 
the side walls (Fig. 4, E). Especially in the wider threads, the protoplast 
appears not uncommonly to protrude in a papillate manner into the thickened 
outer wall (Fig. 4, Z>). The cells have one or two pyrenoids (Fig. 4, 6r). 
Apart from the abundant branching just above the base, the production 
of larger branches in the upper part of the thallus is rare (cf. Fig. 4, A) 
2 
