Although the generic name Sargassum did not enter valid botanical nomenclature until 1820 (C. Agardh, 1820a: 1), it had been used earlier by Rumphius (1750: 188), who in turn derived the name from the Portuguese word sargaço used by sailors to describe the plants floating in the North Atlantic Ocean. Three species referable to Sargassum were grouped by Linnaeus (1753: 1160) in a section of Fucus that he designated ``Ramosi foliis distinctis''. The name Fucus natans was applied primarily to the pelagic Sargassum of the Atlantic Ocean, F. acinarius was intended to apply primarily to the Sargassum of the Mediterranean Sea, and F. lendigerus was given to a collection by Osbeck from Ascension Island in the South Atlantic Ocean. The name Fucus natans was unnecessarily changed to F. sargasso by S. Gmelin (1768: 92), who also (op.cit.: 99) unnecessarily changed the epithet of F. acinarius from an adjective to a substantive, acinaria. The subsequent taxonomic and nomenclatural history of F. natans and F. acinarius is complex.
Fucus natans (``Gulfweed'') was reported from the drift on English shores by early post-Linnaean authors, including Hudson (1778: 573). In his critical review of the fleshy seaweeds of Britain, Turner (1802a) was confronted by these records without having collected F. natans on British shores or having seen such a specimen collected by others. On consulting Linnaeus's herbarium, Turner (op.cit.: 58) concluded that the three specimens determined by Linnaeus as F. natans represented more than one species. After examining morphologically similar specimens sent to him by friends from Jamaica, Bermuda, and the Mediterranean, he described a second species, F. baccifer Turner (op.cit.: 55--60; 1807--1808: 103--107, pl. 47, `bacciferus'), which was later said to occur in all oceans and thence be cast up on the shores of almost every country (op.cit. 103, 105). Although Turner cited F. natans Linnaeus in the synonymy of F. baccifer, he clearly was segregating a second species from the Linnaean concept of F. natans, so that the conclusion that F. baccifer was a superfluous name, as expressed in P. Silva, Meñez, & Moe (1987: 86), is incorrect.
When establishing the genus Sargassum, C. Agardh (1820a: 6) disagreed with Turner's interpretation of Fucus natans and treated that name and F. baccifer as synonyms, but unfortunately he confused the nomenclature by adopting the later name (as Sargassum bacciferum). Fucus natans sensu Turner (1802a: 48--55; 1808: 99--103, pl. 46) was accommodated by a new species, Sargassum vulgare C. Agardh (op.cit.: 3), but that name was initially superfluous since Agardh included in its protologue F. salicifolius S. Gmelin (1768: 98; syntype localities: various, including Rodosto [TekirdagBe], Turkey).
Børgesen (1914a: 7--11) reassessed the three authentic specimens of F. natans in Linnaeus's herbarium. He designated as type [lectotype] the best-preserved specimen (op.cit.: fig. 3), which is the one that most closely resembles Turner's illustration of F. baccifer (Turner, 1807--1808: pl. 47). On this sheet Linnaeus has written ``Indica'', probably referring to Jamaica. A second specimen, which Turner indicated as belonging to F. baccifer var. oblongifolius (Turner, op.cit.: 103--106, said to be sympatric with the nomenclaturally typical variety), appeared to Børgesen to approach the pelagic form that he described as S. hystrix J. Agardh var. fluitans Børgesen (op.cit. 11, fig. 8; type locality: Sargasso Sea). He later elevated this taxon to specific rank, as S. fluitans (Børgesen) Børgesen (1914b: 66, footnote). The third specimen, poorly prepared, was determined as F. natans by Turner and considered by Børgesen to be conspecific with the first specimen. Børgesen, like C. Agardh, concluded that F. baccifer and F. natans are taxonomic synonyms, but unlike Agardh he adopted the Linnaean epithet. He omitted the combining author, however, in the absence of information about the person who first made the combination. To my knowledge this person is Gaillon (1828: 355), who published the combination a few months (May vs. August) ahead of Naccari (1828: 98). Both authors, however, cited Fucus natans Turner rather than F. natans Linnaeus as the basionym, presenting the possibility that they were following C. Agardh in subsuming the Linnaean name under F. baccifer and treating F. natans sensu Turner as a different species (Sargassum vulgare C. Agardh). If this interpretation is adopted, Sargassum natans Gaillon becomes a legitimate name for the species based on Turner's plate 46 and precludes the transfer of F. natans Linnaeus to Sargassum, thus allowing S. bacciferum to remain as the correct name of the species that includes the type of the Linnaean name. These nomenclatural consequences would be so confusing as to provide strong support for proposals to conserve or reject one or another name in order to achieve some measure of stability. It should be noted that no one seems to have lectotypified F. baccifer from among the various specimens that Turner had at his disposal.
Fucus acinarius was said by Linnaeus to occur ``in Italia & Oceano australiori''. He cited three references to Mediterranean plants, including ``Acinaria imperati'' Donati (1750: XXXV, pl. IV: fig. A, as Acinaria con caule terete, con li rami inferiori compressi, e con li superiori rotondi, Acinara, o Agresto marino dell'Imperato). It seems logical to lectotypify F. acinarius with the Adriatic plant described and illustrated by Donati, and S. Gmelin (1768: 99--100) accordingly treated the species as being restricted to the Mediterranean. As an epithet, however, he used the substantive Acinaria rather than the adjective acinarius used by Linnaeus. The adjectival epithet was restored by Setchell (1933a: 208). Turner (1807--1808: 109--111, pl. 49), alluding to his reliance on the authority of the Linnaeus's herbarium (and questioning whether it was well founded), stated that the Mediterranean plant was the species ``to which there can be no question but that Linnaeus himself originally intended to apply that name [Fucus acinarius]''. Without explanation, however, he changed the name of the Mediterranean species to Fucus linariifolius (derived from Fucus folliculaceus, linariae folio C. Bauhin, one of three Mediterranean references cited by Linnaeus) and applied F. acinaria to a species said to occur in the Red Sea, East Indies, and the Korea Strait. Later, Turner (1809--1811: 83--85) changed the name F. linariifolius to F. linifolius and stated that Linnaeus had a plant in hand from the East Indies while intending to describe a common Mediterranean species. When establishing the genus Sargassum, C. Agardh (1820a: 22) followed Turner in applying the epithet acinaria (as Sargassum acinaria) to a non-European species, while the Mediterranean portion of F. acinarius was assigned to Sargassum linifolium (Turner) C. Agardh (op.cit.: 18). Sargassum acinaria must be attributed to C. Agardh and considered an illegitimate new name for F. acinarius Linnaeus. J. Agardh (1889: 114), without explanation, cited the name as S. acinaria (Turner) J. Agardh.
The application of the name F. acinarius was addressed by Setchell (1933b: 209--210) with reference to Linnaeus's herbarium. He found that two unlike specimens had been mounted on a single sheet labeled ``acinarius'' but without collecting data or any indication of the date of insertion in the herbarium (op.cit.: pl. 39). Setchell suspected that ``the right-hand Linnaean specimen may be a rather narrow-leaved form of the Mediterranean species, S. linifolium (Turn.) Ag., which Linnaeus undoubtedly had in mind when he founded his Fucus acinarius, and to which, despite Turner's scruples, the name of Sargassum acinarium undoubtedly belongs''. In restoring Linnaeus's adjectival epithet, Setchell incorrectly retained C. Agardh as the combining author.
Setchell (op.cit.: 210--212) attempted to find the specimen from which Turner's plate 49 was drawn, but found nothing at Kew with such an indication. The specimen most similar to plate 49 was one labeled ``Herb. Turner, var. of F. Swartzii?'' (op.cit.: pl. 40), which Setchell determined as S. acinaria C. Agardh var. crassiusculum Grunow (1916: 155 [``crassiuscula'']; type locality: China Sea). He then made the combination S. swartzii var. crassiusculum (Grunow) Setchell (op.cit.: 211).
As in the case of S. natans, S. bacciferum, and S. vulgare, the competing and confusing applications of the names S. acinaria and S. acinarium should be settled by means of proposals for conservation or rejection.
Sargassum was lectotypified with S. hornschuchii C. Agardh (1820a: 40; type locality: Parenzo [Porec], Croatia) by De Toni (1891: 174), but when conserved against Acinaria Donati (1758: 26, 33), S. bacciferum (Turner) C. Agardh was selected as the conserved type.