Note: Sargassum, like Caulerpa, is burdened with a cumbersome classification and nomenclature as a result of attempts to give taxonomic recognition to every morphological variant. In Sargassum, however, the causes of variability are more numerous than in Caulerpa and include position on plant (basal or apical), sexual dimorphism, ontogeny, seasonality, environmental factors, random phenotypic expression, and geographically correlated genotypic differences (Kilar, Hanisak, & Yoshida, 1992). Taxonomists have only recently begun to analyze this variability by using modern techniques, such as biometrics, culturing, outplanting and transplanting, karyology, experimental hybridization, chemotaxonomy, molecular taxonomy, and numerical taxonomy (e.g., Kilar et al., 1992).
Art. 24.1 states that "The name of an infraspecific taxon is a combination of the name of a species and an infraspecific epithet connected by a term denoting its rank''. In other words, the name of an infraspecific taxon is a trinomial. For purposes of nomenclature, there are no quadrinomials or quinquenomials. The example given under Art. 24.1 makes it clear that in writing Sargassum ilicifolium var. conduplicatum forma erythraeum, Grunow (1915 [1915–1916]: 406) was giving the taxonomic opinion that his new form of S. ilicifolium should be placed under the variety conduplicatum. For purposes of nomenclature (as distinguished from taxonomic opinion) this name should be expressed simply as S. ilicifolium forma erythraeum. Moving this form to any other variety of S. ilicifolium does not require a new combination, contrary to current practice. Thus, we can write S. ilicifolium var. ilicifolium forma erythraeum Grunow or S. ilicifolium var. lasgoriense forma erythraeum Grunow. In this catalogue, the varietal placement of a form is enclosed in brackets to emphasize that it is a taxonomic statement rather than a nomenclatural act.
Sargassum acinaciforme Montagne, 1850a: 239–241 (type locality: Hodeida, Yemen).—Børgesen, 1939b: 99.— S. Dixit, 1970: 115.— Basson, 1992: 221.
INDIAN OCEAN DISTRIBUTION: Iran.