10 HENRIK PRINTZ [1920 



lo the orientation of Ihe cells to the substratum. The chromatophore 

 is a parietal bell, which covers the whole of the iniier cell-wall; 

 il is without a pyrenoid. 



I have often observed thai the contents of the oells by succe- 

 daneous divisions are divided iiito a great nuinber of daughter cells, 

 escaping through a hole in the mother membrane. Thus, in this 

 variety the old membrane doss not dissolve into mucilage, which 

 seemis to be the usual way in this genus according to the information 

 on this subjcct in the literature, for instance by Lagerheim, 

 Reinsch, and De Toni, and empty mother membranes (pi. II, 

 fig. 80 and 81) are frequently to be found in preparations of 

 this alga. As long as Ihese daughter cells, which must probably be 

 designated as aplanospores, are lying within the mother membrane, 

 as aiso at the moment of escaping it, they are entirely smootli. 

 Their size is about 2—2,5 u in diameter. The smallest Acanfhococcus- 

 cells I have been able to recognize by the structure of the membrane, 

 measure about 3 — 4 u in diameter. In so small cells the membrane 

 is only very slighlly'crenulale, however (vide fig. 89. pi. II), and the 

 structure can be seen by a very close examination only. Whether the 

 small oells on having escaped the mother membrane, are further 

 divided and undergo a Pa/jne/Za-stage, or the like, or whether they 

 are real aplanospores directly increasing and growing out into new 

 i4canfhococcus-cells, I have not had sufficient material to asoertain. 

 Personally I am of opinion that the last mentioned Ihing happens, 

 as I have not obsei^ed anything that may be explained as divisions 

 or PalmeHa-stages. 



As kiiown, the genus Acanthococcus is oonsidered to be a very pro- 

 blematic one, and several of the species described as Acanthococcus 

 are no doubt only resting cells or phases of development belonging 

 lo other algae. It is, however, beyond a doubt that sonie of them, 

 al least, are entirely independent species of algae. If the small cells 

 observed by me, escaping Ihe mother membrane, should turn out to 

 be real aplanospores, this genus is to be refem-e/d to the family of 

 Oocystaceae, where ils neare&t relations must be sought among the 

 Chlorella or allied genera. 



This species seems to be a very common aérophilous alga in the 

 neighbourhood of Durban. Thus, I have found it in quite a number 

 of samples: 37, 99, 105, 109, 122, 134, 138, 171, 237, 252, 272, 279, 

 and 313. 



Hormidium flaccidum Braun in Rabenhorst, Algen (1876) no. 

 2480. Hormiscia fhiccida (KiJTZ.) Lagerheim in Flora 1888, no. 4; 

 De Toni, Syll. Alg. I, p. 161. [PI. VI, Fig. 233-2431. 



Specimens of this extremely varying and yet by far not eluci- 

 dated species or coUective species I have found in some samples 

 from the environs of Durban (nos. 16, 19, 26, and 238). 



