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



39 



filaments from the lowermost part of the spore. These fila- 

 ments consist of a few cells only and lie along the surface of 

 the host in which they are not imbedded, or at the most only 

 a little on their lower side. From the cells in these creeping 

 filaments erect ones were found growing up in a few vigorous 

 specimens (Fig. 36 b). The spore itself is quite globular, about 

 17// in diameter; it lies upon the surface of the host plant. The 

 plants are mostly fixed at the 

 base of the pinnules of the host 

 and many plants are often found 

 surrounding each pinnule (Fig. 

 36 a). Most probably the ger- 

 minating spore finds more shelter 

 here. But plants occur also on 

 other parts of the host and 

 even upon the pinnules them- 

 selves. From each spore a single 

 (or in more vigorous plants two 

 or more) erect filaments grow 

 up. They consist of cylindric 

 cells ; ' in the basal part their 

 diameter is about 8 — 9 — 11 yt, 

 higher up the diameter increases 

 and in vigorous plants it reaches 

 a length of 13—14 [x. The 

 length of the cells is often 80 fi 

 and more. Towards the sum- 

 mit the filaments again taper, 

 their diameter reaching only 

 6 — 7/i, but the ends are not 

 hairlike and the cells contain 

 both chromatophore and pyre- 

 noid (Fig. 35). 



The chromatophore (Fig. 37) 

 is parietal, often with long prolongations along the wall of the 

 cell and it contains a large lateral pyrenoid protruding markedly 

 into the interior of the cell. 



The ramification begins from near the base but is further 

 developed higher up. It is multilateral and the branches ramify 

 copiously in the same manner. 



The sporangia (Fig. 35, 37) are oblong-oval or more elong- 

 ated, subcylindric or subclavate. They are mostly sessile but 



Fig. 35. Acrochætium opeligenuin 



nov. spec. Small part of an erect 



ramified filament. (About 90 : 1). 



