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



331 



This plant has been found partly in shallow water (about one 

 meter) in a rather exposed place and partly in deep sea at a depth 



of about 30 meters. 



St. Croix: White Bay. St. Tho- 

 mas: In the sea to the west of Water 

 Island. 



Geogr. Distrib.: Mexico, West 

 Indies. 



Fig. 331. Dictyurus occidentalis J . Ag. 

 a, part of a small poorly developed erect shoot showing the growing 

 together of the net. b, part of the thallus. (a, about 20:1; b, 6:1). 



Genera incertae sedis. 



Falkenbergia Schmilz. 



1. Falkenbergia Hillebrandii (Bornet) Falkenb. 



Falkenberg, P., Rhodomelaceen, p. 689. Børgesen, F., Some new 

 or little known W. I. Florideæ. II, (Bot. Tidsskr., vol. 30, p. 199). Col- 

 lins and Hervey, Alg. Bermuda, p. 122. 



Poly s iphonia Hillebrandii Bornet in Ardissone , Phycologia Mediter- 

 ranea, I, p. 876. 



The genus Falkenbergia is remarkable for its 3 pericentral cells and 

 especially for its way of branching, this being, as pointed out by Fal- 

 kenberg, very different from the two ordinary ways of branching, 

 either exogenous or endogenous, in the Rhodomelaceæ. The branching 

 takes place in such a manner that a cupola-formed outgrowth is 

 given off from the middle of one of the pericentral cells ; this out- 

 growth is soon separated from the mother cell by a wedge-shaped 

 wall becoming the apical cell of the new branch (Fig. 332 c). The 



