Nr. 1] SUBAERIAL ALGAE FROM SOUTH AFRICA 21 
thus give completely deceptive results. Only in this way it will be 
possible to get rid of the old «Pleurococcus-problem». 
The species occurs as åa greenish coating on the bark of trees in 
some samples from the environs of Durban, where it seems to be ol 
rather frequent occurrence (16, 52, 85, 302, 303), and in one single 
sample from Ostenwald, Saldanha Bay (356). Akinetes have been 
found in the samples 16 and 302. 
Pleurastrum lobatum (CHopaT) Printz nov. comb. |PI. VI, 
Fig. 156—2001. 
Under the name of Pleurococcus lobatus, Cnopar, in his work 
Ålgues Vertes de la Suisse, 1902, p. 284, has described a species that 
Is characteristic in having rather tumid and roundish cells, 
because of which they also rather rapidly disintegrate after the 
divisions. It is further characterized by its chromatophore and by 
wanting a pyrenoid. This alga I have also met with very frequently 
in a number of the samples from South Africa. On account of the 
fact that the cells are rounded off and disintegrate rather quickly 
after the divisions, larger and pluricellular colonies are only rarely 
to be met with. Ås a rule only solitary spherical cells or colonies 
consisting of 2—3 or 4 cells, such as the uppermost figures of pl. IV, 
are to be found. In some few samples, however, I have met with 
larger colonies of this species. It then appears that the cell divisions 
of this alga-are not regular «Pleurococcus-divisions», that is, in all 
ihree directions, and whereby the characteristic «Pleurococcus- 
packages» are formed. The cell-divisions of this alga, on the con- 
trary, proved to take place in two directions only, whereby cell- 
plates are formed. PI. IV, nethermost, shows å number of somewhat 
larger colonies, where this fact is clearly observed. Fig. 196—197, 
and 198—199 show two colonies respectively in face and "side Views. 
J. BoyE-PETERSEN, Studier over danske aérophile alger 1915, 
s. 921, has already pointed out the same feature with regard to this 
species. Cfr. his pl. I, fig. 10. This is, besides, also noticeable 
on other drawings of the species in question. Thus, Wirce has 
found the same alga in samples from Hawaii, collected by dr. 
RECHINGER, and in his work, Silsswasseralgen von den Samoain- 
seln etc., 1914, the figure (pl. III, fig. 1) of this species also 
distinctly shows that the cells are lying in the same plane. 
In the work by Boyre-PETERSEN, quoted above, the author mentions 
that he seems to have observed zoospores in cultures of Pleurococcus 
lobatus. However, as he is not quite sure that this culiures were 
absolutely pure, he does not dare to maintain with certainty that 
the zoospores he has seen, really originate from P. lobatus, but 
may possibly have been produced by another species. In my 
material from South Africa, however, I have been able to point 
out with eertainty zoospores in this alga, as I have found that the 
