The Freshwater Algae of Africa. 535 



Genus GONGROSIRA Kuetzino. 

 1. Gongrosira disciformis,n. sp. (Fig. 18.) 



Thallus epiphyticus, plantis aquaticis adhaerens, calce incrustatus, 

 densus, forma disci circularis vel saepe valde irregularis, diametro raro 

 plus quam 1 mm. ; in sectione transversa plus minus deplanato-con- 



Fvi L8 —Gongrosira disciformis, n. sp. A. Small part of the surface of 

 the Myriophyllvm showing the form of the thalli of the epiphyte. 

 /; Section through the surface of the substratum, showing a part of 

 on e of the convex cushions. C. Small part of the edge of a thallus 

 seen from the surface 4 x 12; B and x 375. 



vexus (altit. max. 50 /v.). Pars procumbens thalli e filis valde ramosis 

 (ramis brevibus interdum imperfecte segregatis), parenchymatice 

 aggregatis, constans. Pars adscendens e filis uumerosis brevibus 

 erecte vel oblique dispositis, cum parte procumbente pulvinulum 

 densum efficientibus. Cellulis, diam. ca. 9-12 //, 1-2-plo longioribus 

 quam iatis, membrana modice incrassata, forma variabili, granulis 

 amylaceis parvis confertis, pyrenoidibus ? 



