The Freshwater Algae of Africa. 



583 



from the base to the apex (Fig. 38, A and G), and, amongst these, 

 comes nearest to D. baueriana (Grun.), Bornet et Flahault and D. 

 olivacea (Hooker), Bornet et Flahanlt ; from the former it differs in 



t'ni. 39. — Vichothrix spiralis, n. sp. A. View of an entire (small) plant to 

 show the genera] habit. />'. Small portion more strongly enlarged. 

 C. Base of a trichome, with a heterocyst. D. Part of a filament 1" 

 show the frequent spiral coiling of the trichomes. A x GO ; B x 330; 

 C and D, x 660. 



the character of the sheath and the absence of a terminal hair to the 

 trichomes, from the latter in the same respects, as well as in the 

 nature of the cell-contents. 



2. Dichothrix spiralis, n. sp. (Fig. 39.) 



Filis in caespites irregtilares ad 1500 fi longos aggregatis, plantis 

 affixis, e basi angusta patescentibus ; lilis et pseudoramis pins minus 



