F. Børgesen: Rhodophyceæ of the Danish VV. Indies. 



55 



new endophytic filaments while upwards from their upper ends 

 the assimilating and spore-bearing filaments arise. In this way 

 the endophytic filaments form together proportionally dense clu- 

 sters as most of the filaments run downwards nearly side by side ; 

 but now and then also endophytic filaments are found which 

 bend outwards to the side, thus giving rise to new tufts in a 

 similar way to that described by Rosenvinge for Acrochætiiim 

 Nemalionis. But in Acrochætiiim phacelorhiziim it seems to be not 

 so common. The endophytic filaments reach a thickness of up to 

 27 fji and the length of the cells is about 

 36/^. Most often they are thickest at the 

 lowermost end tapering gradually up- 

 wards. The wall of the filaments is often 

 somewhat sinuous. 



From the upper end of this rhizome- 

 like base the erect filaments arise as men- 

 tioned above forming a more or less dense 

 cluster; in a vigorous plant about 4 — 6 

 filaments are present; the remnants also 

 of several broken off or dead filaments 

 are often to be found. 



The erect filaments (Fig. 58) have 

 spreading branches, in the upper part 

 with some tendency to unilaterality. The 

 filaments are thickest in the lowermost 

 part, about 11 — 12 fx, tapering very grad- 

 ually towards their summit, being here 

 about 6/z thick; these thin ends of the 

 filaments die gradually away. In spec- 

 imens still in vigorous growth the fila- 

 ments have blunt ends and do not taper 

 so much. In the lowermost part the cells 

 are about 40 /x long, being mostly a little 



longer upwards, about biju. The cells are cylindrical and not 

 constricted at the transverse walls. They contain a parietal 

 chromatophore (Fig. 59) with a large pyrenoid protruding con- 

 siderably into the interior of the cell. 



In the .specimens found the sporangia were not present in 

 great number. They occur often a few together seriately near 

 the base of the branches but, often also quite scattered (Fig. 58). 

 All the sporangia found were sessile and monosporous, oblong, 



Fig. 57. Acrochæliwn 



phacelorhizum nov. spec. 



Two basal parts. 



(About 100 : 1). 



