The nomenclature of the species usually, but incorrectly, called Stilophora rhizodes (Turner) J. Agardh (1841: 6) is intricate while its taxonomy is uncertain. The species has traditionally been considered to begin with Fucus rhizodes Turner (1815--1819: 91--93, pl. 235), the epithet being adopted from the manuscript name Conferva rhizodes used on specimens distributed by Jakob Friedrich Ehrhart (1742--1795), a German botanist and pupil of Linnaeus. The name Fucus rhizodes is superfluous and hence illegitimate, however, since Turner listed two legitimate names in synonymy, Ceramium tuberculosum Roth (1800b: 162--164) and Conferva gracilis Wulfen (1803: 21). As a third synonym he listed Conferva verrucosa J.E. Smith (1807 [1790--1814]: pl. 1688; type locality: Southampton, Hampshire, England), but this name is a later homonym of Conferva verrucosa Mohr (1803: 474; type locality: Göttingen, Lower Saxony, Germany), a name of an unknown freshwater alga. Turner was not the first to establish a species to accommodate Ehrhart's unpublished name, however, as C. Agardh (1811 [1810--1812]: 18) did so a few years earlier when he described Ceramium rhizodes. Like Turner, C. Agardh cited Ceramium tuberculosum Roth as a synonym so that Ceramium rhizodes is also a superfluous name.
In accordance with Art. 7.5, the type of both Ceramium rhizodes and Fucus rhizodes is the type of Ceramium tuberculosum Roth, the earliest legitimate synonym cited in their protologues. Ceramium tuberculosum was based on specimens from the Adriatic sent to Roth by Wulfen. To judge from a comparison of protologues, Conferva gracilis Wulfen (1803: 21) would seem to have been described from specimens similar to those sent to Roth, and in fact Roth (1806: 112--113) placed Conferva gracilis in the synonymy of his Ceramium tuberculosum. While it is not likely that the specimens sent to Roth are extant (see Stafleu & Cowan, 1983: 916), their identity is of no practical significance since the transfer of this species to Stilophora would create a later homonym of Stilophora tuberculosa Reinke (1889a: 72), a name applied to a species considered by Reinke to be distinct from S. rhizodes. The epithet tuberculosa was adopted from Ceramium tuberculosum Roth, not as to type, but as interpreted by Hornemann (1816: pl. MDXLVI). Hornemann's interpretation of C. tuberculosum had previously been described as a new species, Chaetophora nodulosa C. Agardh (1817: 127), and this name was cited in the synonymy of Stilophora tuberculosa Reinke, making the latter name superfluous. In accordance with Art. 7.5, the type of S. tuberculosa Reinke is the type of Chaetophora nodulosa C. Agardh.
Another name that comes into consideration is Fucus tenellus Esper (1800 [1797--1800]: 197, pl. CIX). Esper based this species, as well as F. tenerrimus Esper (op.cit.: 198, pl. CX) and F. tenuissimus Esper (op.cit.: 199, pl. CXI), on material sent to him by Wulfen. Because Wulfen (1803: 62) gave an account of these species under these names without mentioning Esper, it is reasonable to assume that he had written these names on specimens that he sent to Esper. Wulfen also stated that the material for these three species came from Trieste. Fucus tenerrimus has not been mentioned by subsequent authors, but Esper's illustration may be referred with little doubt to the species described as Chondrosiphon mediterraneus Kützing (1843b: 438, pl. 53.III; type locality: Napoli, Italy) and Chylocladia polycarpa Zanardini (1876: 533--534, pl. XXVIII.A [CX.A]; type locality: Piran, Slovenia). According to Hauck (1883 [1882--1885]: 156) and Kylin (1931: 27), Chrysymenia firma J. Agardh (1842: 107; type locality: Pozzuoli, near Naples, Italy) is an earlier name for this species, which was transferred to Chylocladia by J. Agardh (1851 [1851--1863]: 363) and to Lomentaria by Falkenberg (1879: 271). Kylin (l.c.) retained the latter placement.
Fucus tenellus, like F. tenerrimus, has not been mentioned by subsequent authors, but Esper's illustration is clearly referable to the species traditionally called Stilophora rhizodes (Turner) J. Agardh.
Fucus tenuissimus, the only one of the three species to be mentioned by subsequent authors, was considered by Turner (1811--1819: 4, 5) to be very closely related to Fucus crinalis Turner (Gelidium crinale (Turner) Gaillon (q.v.)), but he fell short of citing it as a synonym. (`` ... I can scarcely persuade myself that the two plants are more than varieties of each other.'') Dixon & L. Irvine (1977b: 126) treated G. crinale as a form of G. pusillum (Stackhouse) Le Jolis (q.v.), although traditionally the two species have been kept apart. Fucus tenuissimus was transferred to Gelidium by Trevisan (1845: 17), but because it is a later homonym of F. tenuissimus Withering 1796 (treated as a nomenclatural synonym of Chondria capillaris (Hudson) Wynne q.v.), the binomial Gelidium tenuissimum must be accredited directly to Trevisan and considered a nomen novum in accordance with Art. 58.3. In summary:
Stilophora tenella (Esper) P. Silva, comb. nov. Basionym: Fucus tenellus Esper (1800 [1797--1800]: 197, pl. CIX).
WARNING! see information about new combinations.
Stilophora nodulosa (C. Agardh) P. Silva, comb. nov. Basionym: Chaetophora nodulosa C. Agardh (1817: 127).
WARNING! see information about new combinations.
Lomentaria tenerrima (Esper) P. Silva, comb. nov. Basionym: Fucus tenerrimus Esper (1800 [1797--1800]: 198, pl. CX).
In trivial ways, the nomenclature of Stilophora has been complicated by the confusion of the epithet tuberculosa with tuberculata (as by Parke & Dixon, 1976: 560) and the confusion of Ehrhart with Ehrenberg (as by Al-Hasan & Jones, 1989: 296).
Reinke (l.c.) suggested that S. tuberculosa as well as Halorhiza vaga Kützing (1843b: 335) might be young stages of S. rhizodes. Whether there are two or only one species of Stilophora in the North Atlantic and Mediterranean remains to be settled.