Adiantum furcatum L. f.

Callmander, Martin W., Mazumdar, Jaideep & Jarvis, Charles E., 2019, Typification and nomenclature of the western Indian Ocean islands ferns and lycophytes described in Linnaeus filius’s Supplementum plantarum, Candollea 74 (2), pp. 223-234 : 229-232

Adiantum furcatum L. f. , Suppl. Pl.: 447. 1782.

Lectotypus (designated here): RÉUNION: “40. de l’Isle de Bourbon ”, s.d., Commerson s.n. ( LINN-HS nº 1629.15 image seen ; isolecto-: G [ G00341871 ]!, MPU [ MPU018221 ]!) ( Fig. 6 ) .

= Asplenium rutifolium (Berg.) Kunze in Linnaea 10: 521 (1836). ≡ Caenopteris rutifolium Berg. in Acta Petropol. 1782: 249. 1786. ( Aspleniaceae )

Notes. – The protologue of Adiantum furcatum included references to PLUKENET (1700: 83, tab. 350, fig. 4) and to two specimens as “Thunberg. Thouin” with the mention “Habitat in Cape. Bonae Spei & Insula Helenae”. Two specimens of original material are extant in LINN-HS: a specimen collected by Carl Peter Thunberg (1743–1828) in the Cape region [LINN-HS nº 1629.16] with duplicates in SBT [SBT10616] and UPS [UPS-THUNB nº 24774], and a specimen from Réunion originating from Thouin’s shipment in 1780 (see above) [LINN-HS nº 1629.15]. SWARTZ (1801, 1806) excluded the reference to “Filicula corniculata Insulae Sanctae Helenae” of PLUKENET (1700) which refers to a species of Elaphoglossum Schott ex J. Sm. , E. bifurcatum (Jacq.) Sw. , a fern endemic to St. Helena. CHRIST’s (1899) transfer of Adiantum furcatum to Elaphoglossum (as E. furcatum (L. f.) Christ) is a nom. illeg. currently treated as a synonym of E. bifurcatum (Jacq.) Sw. ( ROUX, 2009; VASCO et al., 2009).

The two specimens of original material extant in LINN-HS where Linnaeus f. added “Adianthum furcatum” are identifiable as a species of the genus Asplenium L. The combination of Adiantum furcatum in the genus Asplenium would be illegitimate, as it is preoccupied by Asplenium furcatum Thunb. (= A. aethiopicum (Burm. f.) Bech. ). Linnaeus f.’s name should be treated as a synonym of Asplenium rutifolium ( TARDIEU-BLOT, 1958), the first available name in the genus. Its basionym, Caenopteris rutifolium , was described by Peter Jonas Bergius (1730–1790) based on a Thunberg collection in SBT [SBT10616], a duplicate of original material (isosyntype) of Adiantum furcatum .

The Commerson s.n. collection [LINN-HS nº 1629.15] (bearing the number “40” corresponding to the younger Linnaeus manuscript list sent to Thouin) is here designated as lectotype. It is chosen over the Thunberg collection as Linnaeus f. added to the label “Adianthum furcatum ny”. Duplicates of original material are extant in G [G00341871] and MPU [MPU018221].

Asplenium rutifolium is distributed in Mauritius, Réunion, Madagascar, the Comoro islands and the Cape region to Malawi and Yemen in Continental Africa ( TARDIEU-BLOT, 2002).

Figures

Fig. 6. – Lectotype of Adiantum furcatum L. f. in LINN-HS).