536 Annuls of the Smith African Museum. 



Samples 29a (here largely overgrown by Cyanophyceae), 30a (in 

 both cases on Myriophyllum) . 



This species forms small white spots on the surface of the stems of 

 Myriophyllum. These spots, which are readily recognisable with the 

 naked eye, sometimes appear rounded, but more often they are like 

 streaks or even highly irregular in shape (Fig. 18, A), which is 

 probably in part due to confluence of thalli. They rarely extend for 

 more than 1 mm. in any direction. In transverse section (Fig. 18, B) 

 they appear as flattened convex cushions, closely adpressed to the 

 substratum. 



The details of construction are only easily deciphered, after the 

 plentiful incrustation of carbonate of lime has been removed with weak 

 acid. A richly branched system of threads creeps on the substratum 

 (Fig. 18 G) and gives origin to numerous erect or obliquely ascending 

 short branches which, together with the creeping system, form the 

 disc-like thalli (Fig. 18, B). I have been unable to establish certainly 

 wdiether the upright threads are branched, but the procumbent ones 

 branch again and again, with the result that an almost parenchy- 

 matous stratum (Fig. 18, C) is produced, in which the individual 

 threads are only plainly distinguishable near the edge. Some of the 

 short branches are not completely separated off from their relative 

 main axis. It appears that all the branches are held together by a 

 matrix which remains after decalcification. 



The cells are of varying shape, often longer than broad, and have a 

 moderately thick membrane (Fig. 18, C). They were crowded with 

 numerous small starch-grains which rendered all other features of the 

 cell-contents obscure. 



This species seems to come nearest to G. schmidlei, P. Richter 

 (Neue Algen de Phyk. univers., fasc. xiii, Hedwigia, xxxiv, 1895, 

 j>. 22, tigs, a, h, c), which, however, forms larger and more convex 

 cushions. Other points of difference are : (a) The abundant ramifica- 

 tion of the upright branches; (h) the often greater length of the 

 cells; and (c) the absence of contents in the lower cells of the 

 branches. 



Genus APHANOUHAETE A. Bkaun. 



(HERPOSTEIRON Naegeli.) 



1. Aphanochaete repens, A. Braun, Betracht. ueb. d. Erschein. d. 

 Verjueng., etc., 1851, p. 196, footnote. (Syn. : Herposteiron confer- 

 vicola, Naeg. ). 



