36 HENRIK PRINTZ [1920 
divisions are rather regular, the colonies arisen get a very 
regular appearance, with nearly equally large, cubical cells, lying in 
regular rows. The cireumference of the colonies is nearly cubically 
rounded. This, which seems to be the typical and full-grown state of 
the alga, measures 16—20 u in diameter. The diameter of the indivi- 
dual cells is 3—4, rarely up to 5 u just before the division. Some- 
times the cell-divisions are somewhat irregular, however, whereby 
are to be found colonies with somewhat larger or smaller cells, and 
also less regularly built. It further occurs that some cells divide 
later on, whereby older families may get a rather irregular appe- 
arance. The original (oldest) cell-walls are usually rather easily 
recognized, however, by their regular run and by unvaryingly 
being somewhat thicker than the younger ones. Such old eolonies 
may reach up to 52 u in diameter. 
The cell-walls, moreover, are comparatively thin and colourless. 
The cells are closely joined to each other, without 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 enelosed by a thin gelatinous investment. 
In the material examined by me, gonidangies were very rare. 
Among several hundreds of colonies which I have examined, 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 in great numbers in gonidangies, which, as 
mentioned, neither in shape nor size differ from ordinary vegetative 
cells. 
Empty cells, which at least partly must be considered as 
emptied gonidangies, I have often observed in my material. 
This alga occurs scattered on bark of trees, in some samples from 
the environs of Durban (mos. 22, 40, and 122). 
In point of external habitus our alga may, to some extent, recall 
the pluricellular spores of certain 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 of the cells into numerous protoplasmic 
bodies — gonidia — which are liberated by the rupture of the old 
membrane. The gradual development of the colonies, traceable 
through the various stages, also favours the supposition of the 
autonomy of this alga. 
Tolypothrix byssoidea (Hass.) KircHn. in EnaGL. et PRANTL, 
Nat. Pflanzenf. Schizophyc. p. 79; De Tonn, Syll. Alg. Vol. V. p. 
551. Hassallia byssoidea Hassatr, British Freshw. Alg. I, p. 283, 
TabNon Eis > 
This species is comparatively common in several of the 
