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 «PZeurococcus-problem». 



The species occurs as a greenish coating on the bark of trees in 

 some samples from the environs of Durban, where it seems to be of 

 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 (Chodat) Printz nov. comb. PI. VI, 

 Fig. 156—2001. 



Under the name of Pleurococcus lobatiis, Chodat, in his work 

 Algues Verfes de la Suisse, 1902, p. 284, has described a species Ihat 

 is characteristic in having rather tumid and roundisli cells, 

 because of which they also rather rapidly disintegrate after the 

 divisions. It is f urther 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 

 faet that the cells are rounded off and disintegrate rather quickly 

 after the divisions, larger and pluricellular colonies are only rarely 

 to be met with. As a rule only solitar^^ spherical cells or colonies 

 consisting of 2 — 3 or 4 cells, such as the uppermost figures of pi. IV, 

 are to be found. In some few samples, however, I have met witli 

 larger colonies of this species. It then appears that the cell divisions 

 of this alga are not regular «P/eurococcas-divisions», that is, in all 

 three directions, and wherebj' 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 a number of somewhat 

 larger colonies, where this faet is clearly observed. Fig. 196 — 197, 

 and 198 — 199 show two colonies respectively in face and side views. 

 ,1. Boye-Petersen, Studier over danske aérophile alger 1915, 

 s. 321, has already pointed out the same feature with regard to this 

 species. Cfr. his pi. I, fig. 10. This is, besides, also noticeahle 

 on other drawings of the species in question. Thus, Wille has 

 found the same alga in sam.ples from Hawaii, collected by dr. 

 Rechixger, and in his work, Siisswasseralgen von den Samoain- 

 seln etc, 1914, the figure (pi. III, fig. 1) of this species also 

 distinctly shows that the cells are lying in the same plane. 



In the work by Boye-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 culiurcs were 

 absolutely pure, he does not dåre to maintain with certainty that 

 the zoospores he has seen, really originale from P. lobatus, but 

 may possibly have been prodliced by another species. In my 

 material from South Africa, however, I have been able to point 

 out with certainty zoospores in this alga, as I have found that the 



