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



221 



The plant grows epiphytically upon larger algæ, e. g. Hali- 

 meda, Udotea, Avrainvillea and forms entangled masses together 

 with Cladophora crispula, Cladophoropsis etc. It is fastened to 

 the host plants by means of rhizoids growing out from the cells 

 in the main filaments, 

 often rather high up 

 in the plants (Fig. 208 

 b) ; the primary base I 

 have not seen. The 

 rhizoids end in small, 

 irregularly shaped discs. 



The plant has no 

 cortical layer. The 

 cells in the main fila- 

 ments are nearly cylin- 

 drical about 2,5 mm. 

 long and 400// broad. 

 The ramification is 

 multilateral or alter- 

 nate, in the upper part 

 of the thallus often 

 secund. A few of the 

 branches grow out as 

 filaments like the main 

 filaments, but most of 

 them become shorter 

 branchlets with definite 

 growth ; these branch- 

 lets are repeatedly 

 pseudodichotomously 

 ramified, having very 

 long cylindrical cells 

 often reaching a length 

 of 3 mm. or even more, 

 while their breadth is 

 only about 100 fj. 



The few tetraspor- 

 angia found were tetrahedrally divided. 



Found in a depth of about 10—12 meters. 



St. Thomas: In the sea to the west of Water Island where in many 

 places it occurred in large quantities. 



Fig. 208. 

 a plant. 



Callithamnion spec, a, upper end of 

 b, part of a filament with rhizoids. 

 (About 40:1). 



