538 



Annul* of the Smith African Museum. 



ponent cells are Large, generally nearly isodiametric (diam. up to 27//), 

 and have a thick gelatinous-looking wall, usually showing prominent 

 si ratification (Fig. 19); the middle lamella sometimes presented a 

 granular appearance. A definite, though delicate, cuticle can with 

 some difficulty be traced round a great part of the periphery of each 

 group. The cell-contents were, highly granular and no details of 

 structure could with certainty be made out, although in material 



Fig. 19. — Chaetopeltis sp. (?). Two typical thalli growing on Dichothrix. 

 Both figures x 500. 



stained with methyl blue there seemed to be a single parietal chloro- 

 plast. 



In general, the arrangement of the ceils displayed no evident regu- 

 larity, but a faint radiate disposition was sometimes recognisable in 

 the subcircular discs. In some cases the cells fitted closely together, 

 without interspaces, but usually they were not so closely arranged 

 (Pig. 11') and even partly overlapped one another. The cells were 

 often in a single layer, though here and there certainly in more than 

 one layer. In some of the thalli certain of the peripheral cells 

 were becoming detached, which may possibly indicate a reproductive 

 phase. 



It will probably be best to defer further discussion of this form 

 until it has been possible to study it more fully. 



