50 
Transactions of the Royal Society of South Africa. 
be a fourth delicate inuermost layer, but it has been impossible to arrive 
at a definite conclusion on this point. The outermost layer is thin, smooth 
and hyaline, the next is somewhat thicker, with a more or less regular 
reticulate sculpturing (Fig. 21, D and E) and apparently yellowish-brown 
colour, whilst the third is very thick, seemingly homogeneous and dark 
brown. The conjugating cells are generally appreciably shorter than the 
ordinary vegetative cells (Fig. 21, C and F), and the cells containiDg the 
zygospores are often in no way inflated (Fig. 21, 0), although here and 
there a slight inflation of the middle portion is apparent (Fig. 21, F). 
The number of chloroplasts is often three (Fig. 21, I), more rarely four 
(Fig. 21, A and B). In the sterile filaments the chloroplasts were fairly 
broad and the pyrenoids often not very conspicuous (Fig. 21, J), but in 
conjugating threads they usually appeared narrower, the pyrenoids forming 
prominent bulges (Fig. 21, B). 
S. subreticulata may also be compared with >S'. cylindrospora, W. & G-. S. 
West, S. horystheriica, Kassan et Smirnoff, and S. imraguayensis, Borge, 
all of which show prominent points of difference. 
3. Spirogyra majtiscula, Kuetzing, Spec. Alg., 1849, p. 441 : Tab. Phycol., 
V, 1855, PI. XXVI, fig. 1. (Syn. : S. orthospira, Naeg. ; Petit, op. cit., 
p. 30, PI. X, figs. 4, 5.) 
Samples 64, 65 (common). 
Lat. fil., 81-87 /x; crass, zygosp., 48-54 /a ; long, zygosp., 72-91 fx. The 
vegetative cells were on the whole relatively short, rarely more than twice 
as long as broad and often not longer than broad. The dimensions, both 
of vegetative cells and zygospores, are larger than those given by Petit 
(he. cit.), but in all other respects the material was quite typical. 
4. Spirogyra hellis (Hass.), Cleve, Svenska Zygnem., p. 18, PI. Ill, 
figs. 2-5; Petit, op. cit., p. 31, PL X, figs. 1-3. (Syn.: Zygnema helle, 
Hassall, Brit. Freshw. Alg., 1845, p. 142, PI. XXIV, figs. 1, 2.) 
Sample 327 (common). 
Lat. fil., 90-96 /X ; crass, zygosp., 51-60 /x ; long, zygosp., 72-84 yu,. The 
form present resembled more closely that figured by Hassall (loc. cit.) 
than that of Petit (loc. cit.), the vegetative cells being very short (as long- 
as broad or 1-|- times as long) and the zygospores having broadly rounded 
ends. It differed from both, however, in showing slightly larger dimensions, 
in the zygospores not so completely filling the fructifying cells, and in the 
fact that the inflation of the latter was quite commonly not very pro- 
nounced. The middle layer of the zygospore-membrane showed a faint 
irregular scrobiculation like that described and figured by Borge (Arkiv f . 
Bot., vi, No. 1, 1906, p. 11, Tab. I, fig. 3). 
5. Spirogyra fluviatilis, Hilse in Eabenhorst, Algen, No. 1476 ; Borge, 
op. cit., p. 27, fig. 33. 
