294 



effaced in older parts of the thallus. In the young parts, on the 

 other hand, it is always very distinct (comp. Fig. 291 a). 



Upon the specimens found only two tetrasporic stichidia were 

 present. The tetrasporangia are formed in the ends of the ramuli. 

 The fertile part consists of 3 4 segments. It is so much swollen 

 that, as pointed out by FALKENBERG, 1. c., "die sterile Stamm- 

 basis dagegen als diinner Stiel scharf abgesetzt erscheint". The 

 fertile part is about 80 // thick. 



With regard to the figures hitherto given intended to por- 

 tray this species, they are all more or less unhappy. I refer to 

 FALKENBERG'S statement concerning this matter. 



Dipterosiphonia dendritica was found growing on a rather ex- 

 posed place and in shallow water. Besides upon Cladophora fuli- 

 ginosa some other specimens have been found upon Laurencia 

 papillosa. 



St. Croix.: White Bay. 



f 



Geogr. Distrib.: Brazil, Australia. 



Subfam. 5. Lophosiphonieae. 

 Lophosiphonia Falkenb. 



1. Lophosiphonia obscura ('Ag.) Falkenberg. 



FALKENBERG, P., Rhodomelaceen, p. 500. 

 Hutehinsia obscura Ag., Spec. Alg., p. 108. 



Polysiphonia obscura J. Ag., Algae Mediterr., p. 123; Spec. Alg., vol. II, 

 pars III, p. 943. 



In the few specimens I have collected the number of the 

 dericentral cells was about 11 12. There was no cortical layer 

 present. 



The plant forms low tufts about 1 3 cm high. The basal 

 creeping filaments are fastened to the substratum by means of 

 numerous short hapters (Fig. 292 a), a single one emerging from 

 each pericentral cell, but often 23 side by side from each seg- 

 ment (Fig. 292 b). The hapters end in irregularly lobed discs. 



The diameter of the creeping filaments is about 150 p. long. 

 From the upper side of the creeping filaments branches emerge, 

 arranged more or less dorsally, the distance between them varying 

 much. Some of these branches bend downwards and fix them- 

 selves to the substratum like the mother filament, but the greater 

 part grow upwards. 



