ECOLOGY AND TAXONOMY OF Halimeda 35 



By 1842 this doubt was resolved, but little more structural work was 

 undertaken until Barton's studies at the turn of this century. Functional 

 and ecological studies had to await the demonstration that Halimeda 

 would grow in culture (Colin vaux et al., 1965) and the availability of 

 modern diving techniques. This article is the first review of these 

 functional and ecological studies. 



III. Basis of the Taxonomy 



The principal theme of this section is the Halimeda species. In it I 

 am concerned with the more obvious ways in which the species vary 

 and how they may be distinguished, rather than with precise details of 

 how one species differs from another. Details of species description, 

 species synonymies and keys to species are therefore reserved for 

 Section IV. Both types of data, however, are brought together in 

 Table X, which summarizes important characters for each of the 

 currently recognized 30 species. The taxonomic information available 

 up to the early 1960s also has been quantified and incorporated into a 

 system of numerical taxonomy developed by Rogers and Fleming (1964) 

 who were then working at the New York Botanical Garden. 



So that the genus may be considered in the framework of the green 

 algae (Chlorophyta) and the plant kingdom, I include a discussion of 

 taxonomic categories above the genus level. 



A. The species 



Barton, as a pioneer in the microscopic taxonomy of this genus, 

 relied principally on one anatomical characteristic, the organization 

 of filaments in a mature node, to distinguish the seven species of 

 Halimeda she recognized (1901). However, with the splitting of some 

 of these species, and the discovery and description of others, such heavy 

 reliance on a single microscopic character is not possible. And if the 

 many new species have validity — there are now over four times the 

 number Barton recognized (Table I) — it follows that reliable characters 

 exist to separate them. For Halimeda many of these are known and 

 tested, and as with most algae they are principally microscopic. 

 However, I have found a few macroscopic characteristics to be reason- 

 ably dependable, and when they are combined with distributional data 

 rehable field identification of some species is possible. These non- 

 microscopic characters can, of course, also be used for laboratory 

 determinations. 



