ECOLOGY AND TAXONOMY OF HaUmeda 



299 



Fig. 99. Clumps of H. macrophysa on a transition buttress on the Islet of Mut, Enewetak 

 Atoll, at depths of 10-15 m. 



the windward side, is the Porolithon ridge, almost a pure stand of 

 encrusting red algae. The growth form of HaUmeda is not adapted to 

 the shock of waves as are those of calcareous reds, but the genus does 

 grow, to some extent at least, in the passages and caverns of the surge 

 channels. These are hung with lush green skeins which include the 

 siphonaceous genus Bryopsis (Fig. 100). Taylor (1950) reports the 

 HaUmeda species opuntia, micronesica and taenicola from this approxi- 

 mate region on other Marshall Islands atolls, and they might well grow 

 on some of the seaward reefs at Enewetak. Somewhat landward from 

 the ridge Taylor also reports opuntia, taenicola, micronesica and tridens 

 { = incrassata), and from the inner reef flat stuposa, opuntia, hikinensis 

 and lacunaUs, the last two in deep holes. 



The part of the seaward reef I could explore most readily was that 

 of the southern tip of Enewetak Islet (south-eastern part of the atoll). 

 Stearns (1945) published on the decadent condition of this particular 



