ECOLOGY AND TAXONOMY OF Holimeda 



37 



Fig. 16. Some of the variability which iTiay occur in segment size and shape shown 

 for H. gigas. Portions of the typical segments, which are reniform to discoidal and 

 very large (Fig. 39), appear in the bottom of the picture, particularly the right-hand 

 corner. The remainder of the segments, which are predominantly cuneate, were 

 produced in culture at light intensities of approximately 125 ft-c. The tips of several 

 of the segments have the whitish cone -like extensions of medullary filaments, 

 indicating that new segments are forming. Scale bar is 10 mm. 



Variations, therefore, do occur. The important point is that the 

 variations do fall fairly well within the range recognizable for each 

 species. I have found that size, shape, texture (and occasionally- 

 colour) of segments may, with care, be used in species identification. One 

 can easily see, for example, that the segments oi macroloba and lacrimosa 

 are very different from those of incrassata or opuntia (Figs 28, 45, 22, 

 19, respectively), and other examples can be found in a study of the 

 species illustrations of Section IV. By contrast, the segments of 

 incrassata and simulans or even of monile and cylindracea may be so 

 similar that identification by segment appearance alone is not reliable. 



The shape of segments may be spherical, to cylindrical, to flattened, 

 with the upper margin of broad flattened segments entire, undulating or 

 lobed, and the lower margin cuneate to auriculate. In size, the range 

 extenss from the small (2-5 mm), tear-shaped segments of lacrimosa to 



