260 F. BORGESEN 



different, being nearly cylindrical with thin walls in our plant, while, in Mme. 

 Weber's plant, they are barrelshaped and thickwalled. 



Now and then groups of hairs occur (Fig. 9 c); the hairs are about 10 \l 

 thick at the base and composed of cells longer than broad; their growth-zone 

 lies a little below the surface of the thallus and consists of quite short cells, 

 densely filled with protoplasm and chromatophores; thence the cells quickly 

 become long and colourless. At their base the hairs are covered by a single 

 or some few sheaths. 



Unilocular sporangia were not present. 



On the other hand I have found some structures (Fig. 9 d) in the upper 

 end of the filaments, similar to those observed by Mme. WEBER who regards 

 them to be plurilocular sporangia. In my material they were not so regularly 

 divided as in the Indian plant. They very much reminded of those found by 

 me in Ralfsia expansa} In spite of a diligent search I have not succeeded 

 in finding emptied plurilocular sporangia, but nevertheless I feel convinced that 

 we have to do with such organs. 



By reason of the thick walls in Mesospora ScJimidtii a bursting of the 

 wall takes place at the formation of the plurilocular sporangia as is easily seen 

 in the drawings of Mme. Weber, in our plant with its thin walls such a 

 bursting is not visible. 



The cells contain an irregularly lobed and bent plate-like chromatophore 

 in which a single or two refractive pyrenoid-like bodies are present. In one 

 of the specimens, sometimes in almost every filament, a cell with homogeneous, 

 yellow brown contents was found. 



Area of distribution: Endemic. 



Ralfsia Berk. 

 R. expansa J Ag. 



Agardh, J., Spec. Alg., vol. t, p. 63. Borgesen, F., Two crustaceous brown 

 algae from the Danish West Indies (Nuova Notarisia, Serie 23, 191 2, p. 123). 



The specimens found are not quite typically developed and I have hesitated 

 to decide whether they are most naturally referable to R. verrucosa or to R. expansa. 

 It must be remembered that Reinke, in »Algenflora» p. 48, mentions that he 

 has found a marked bilaterality in specimens of R. verrucosa from Cherbourg. 



Now, a transverse section of one of the specimens found mostly showed 

 no bilaterality at all while in the other specimen contained in the collection 

 this character vas better developed, being often in good accordance with the 

 figure of Mme. Weber. As compared with my West Indian specimens the 

 Pacific ones had upon the whole a much thinner thallus. 



In one of the specimens unilocular sporangia were present; they were 

 about 24 [j. broad and 65 \l long, in shape and size approaching those I have 

 found in specimens from St. Thomas (1. c. fig. 2 a). At the base of the spo- 

 rangia a small cell was present just as in the West Indian plant; as I have 



1 Compare my figure 148 c in » Marine Algae of the D. W. I.», vol. I, p 191. 



