36 HENRIK PRINTZ [1920 



divisions are ralher regular, tlie colooiies arisen gel a veiy 

 i-egular appearance, with nearly equally large, cubical cells, l^yingin 

 regular rows. The circimiference of the colonies is nearly cubioally 

 rouiided. This, which seenis to be the typical and fuU-grown s/late of 

 the alga, measures 16 — 20 /< in diameter, The diameter of the indivi- 

 dual cells is 3—4, rarely up to 5 /< just before Ihe division. Some- 

 times the cell-divisions are somewhat irregular, liowever, whereby 

 are to be found colonies with somiewhat larger or smaller cells, and 

 also lesis regularly buill. It further occurs that some oells divide 

 later an, whereby older famiilies may get a rather irregular appe- 

 arance. The original (oldest) cell-walls are usually rather easily 

 recognized, however, by their regular run and by mivaryingly 

 being soinewhat thicker than the yomiger ones. Sucb old colonies 

 may reach up to 32 u in diameter. 



The cell-walls, moreover, are comparatively thin and colourless. 

 The cells are closely joined to each olher, wilhout intercellular 

 spaces, whereby the cells mostly get an angular-cubic appearance. 

 The peripheric cells, however, commonly have somewhat tumid 

 outer walls. The contents of the cells are greyish-violet, without 

 vacuoles. The colony is enclosed by a thin gelatmous investment. 



In the material exammed by me, gonidangies were very rare. 

 Among several hundreds of colonies which I have exammed, I have 

 found only two with gonidies. This discovery is of great importance 

 for elucidating the systematic position of the alga. The gonidies are 

 very small, and arise m great numbers in gonidangies, which, as 

 mentioned, neither in shape nor size differ from oitlinary vegetative 

 cells. 



Empty cells, which at least partly must be considered as 

 cmptied gonidangies, I have often observed in my material. 



This alga occurs scattered on bark of trees, in some samples from 

 the environs ol Durban (nos. 22, 40, and 122). 



In point of external habitus our alga may, to some exleiut, recall 

 the pluricellular spores ol oertain lichens. It is, however, even on 

 dried material readily distinguished by the characteristic greyish- 

 violet colour, the delicate gelatinous envelope, and, above all. the 

 divisions of the contents ol the cells into numerous protoplasmic 

 bodies — gonidia — which are liberated by the rupture ol the old 

 membrane. The gradual development ol the colonies, traceable 

 through the various stages, also lavours the supposition ol the 

 autonomy ol this alga. 



Tolypothrix byssoidea (Hass.) Kirchn. in Engl. et Prantl, 

 Nat. Pflanzenf. Schizophyc. p. 79; De Toni, Syll. Alg. Vol. V. p. 

 551. Hassallia hijssoidea Hassall, British Freshw. Alg. I, p. 283, 

 Tab. 67, Fig. 5." 



This species is comparatively common in several of Ihe 



