52 



As pointed out in my former description this species is an 

 endophyte growing upon Hypnea. I have examined it again 

 and give now a new figure of the basal part (Fig. 53). As the 

 figure shows the base consists of short horizontal filaments 

 creeping in the thick wall of the host. The cells in these fila- 

 ments are short, only a little longer than broad, and from these 

 cells the erect sporangiferous filaments grow upwards often seve- 

 ral together forming in this 

 way small tufts upon the 

 host. 



The erect filaments are 

 not very richly branched 

 (Fig. 54) ; the branches grow 

 out at an acute angle from 

 the mother branch. The 

 ramification is multilateral 

 with some tendency in the 

 upper part to be secund. 



The cells are cylindrical, 

 usually 2 4 times as long as 

 broad. They contain a well 

 developed parietal chroma- 

 tophore (Fig. 54 b) covering 

 nearly the whole wall of the 

 cell and have a large lateral 

 pyrenoid. The sporangia are 

 seriate on the upper side of 

 the branches, sessile or very 

 rarely pedicellate. 



If the basal part is left 

 out of consideration it can- 

 not be denied that the above, 

 described Acrochsetium seria- 



tum shows great likeness to this species. But while the present 

 plant has an endophytic base the other is epiphytic. 



This species has been found in a small lagoon with shallow water. 



St. Thomas: The Harbour. 



Geogr. Distrib. : Danish West Indies. 



19. Acrocliaetium repens nov. spec. 



Thallus e filis endophyticis et filis sporangiferis erectis com- 

 positus. 



Fig. 54. Acrochsetium Hypnese B0rgs. 



A, plant with monosporangia. B, cells 



with chromatophore and pyrenoid. C, 



D, E, hasal parts. (A, about 125 : 1 ; 



B, C, about 250 : 1 ; D, E 200 : 1). 



