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



Ill 



Cutting a transverse section we find that the thallus con- 

 sists in the middle of irregularly most often dichotomously ra- 

 mified cylindrical filaments 

 which run in all directions in 

 the mucilage found here; 

 they have a diameter of about 

 8// but both thicker and thin- 

 ner also occur. 



The peripheral tissue (Figs. 

 119 and 120) reaches a thick- 

 ness of about 90,«, not count- 

 ing the papillæ. The inner- 

 most cell-layer has the largest 

 cells ; these are rounded poly- 

 gonal, rather closely united, 

 about 70// broad and 40« 

 high but larger and smaller 

 ones also occur. The cells 

 in the middle are smaller, 

 roundish, but larger lobed 

 cells are common (Fig. 119 a); 

 the cells in this layer are 

 about 30 iJL high. Between 



Fig. 120. Galaxaura occidentalis noy. 

 spec. Transverse section of the peri- 

 pheral tissue shovving the campanulate 

 chromatophores with the large pyre- 

 noid above. Below the nucleus is maid 

 visible by staining, (About 370:1). 



these cells and the epidermal ones many and 

 often large intervals are present, here the 

 chalk incrustation especially is found forming 

 a circular belt round the whole thallus. 



The epidermal cells are closely united ; 

 they are rounded-trigonal when seen in 

 transverse section (Figs. 119, 120), 5— 7-gonal 

 when seen from above (Fig. 121). They are 

 about 16 /i high and their diameter varies 

 from 18— 30/i. They have a well developed, 

 campanulate chromatophore with a central 

 pyrenoid (Figs. 120, 121). Also in the cell-layer 

 below the cells have chromatophores but less 

 developed while the innermost cells have no 

 chromatophores at all. 



Finally growing out from nearly all the 

 surface cells we find the onecelled papillæ, 

 characteristic to the group of Vepreculæ, by means of which the 

 capacity of the assimilating tissue is so highly increased. The 



Fig. 121. Galaxaura 

 occidentalis nov.spec. 

 Epidermal cells seen 

 from above showing 

 the elegantly shaped 

 chromatophore with 

 the pyrenoid in the 

 middle. 

 (About 500:1). 



