Nr. 1] SUBAERIAL ALGAE FROM SOUTH AFRICA 31 



up to 1,5 mm. in diameter, and are closely appressed to liie 

 substratum. At times they grow so densely that the discs to the 

 naked eye melt together to a cohesive inciiistation of several om.- 

 extent. I liave often observed that where two thalli meet in this 

 way, the}' do not grow into each other. PI. XI fig. 304 shows that 

 then they join closely at the edges, and further growth in this 

 direction ceases. Under these circumstances older discs may, at 

 times, get a somewhat irregular circumference, as the growth con- 

 tinues omly in Ihose directions wiiere there are open spaoes for 

 a continuous growth. The covering ol the stems thus gets Ihin and 

 monostromatic all over, being composed of numerous single discs. 

 From the regular series of cells in each tliallus, however, the lines 

 between the single discs may be easily discemable (vide fig. 293, 

 pi. XI). Subjected to a microscopic examination the species is found 

 to be very characteristic by its regular cells, arranged in radial 

 rows. Already in young and small discs the regular arrangement 

 of the cells in radial rows is to be seen. Towards the circumference 

 the cell rows divide dicliotomously, and in <this way is formed a 

 cohesive disc ol a single layer, without holes or rents. The edge of the 

 thallus is even and entire, always destitute of lobes, and never wilh 

 a tendency to dilapidate into single threads. The individual oellLs 

 are — at least in somewhat older specimens — distinctly rectangu- 

 lar, on an average 1>2 — 2 times as long as broad. The size of the 

 cells is, for the rest, somewhat varying. They aie comparatively 

 smallest on young and small thialli, and measure in full-grown 

 specimens 7 — 9 », The disc-sporangia are somewhat larger and more 

 roundish than the vegetative cells, from nearly globose to ovoid. 

 They occur without order, singly or several together, and any 

 vegetative cell seeims to be able to grow out into a sporangium. Other 

 reproductive organs do not occur in my material. 



When the cell-discs crack, for instance in being tom from the 

 substratum in order to be put under the microscope, they are mostly 

 split up radialh^ along the cell-series. The connection aniong 

 the cells in the disc is evidently stronger between tbe tangential 

 walls, that is, between the individual cells in one and the same 

 row, than between the cell-rows mutually. 



In the course of time quite a number of species of Phycopeltis 

 have been described, partly under other names, as Plnjllactidium, 

 Chromopeltis, Hansgirgia, and others. Several of them, however, 

 seem to have been descrLbed on prunitive and, in systematical 

 regard, dubious charaoters only. It is probable that with the great 

 range of variation which the single species ol this lamily empiri- 

 cally evince, several of these, described as species, in the future, 

 when one day more closely examined and monographically treated 

 accordmg to modern principles, will tum out only to be modifi- 

 cations due to habitats, and that the number of true, systematically 



