Didymoglossum erosum (Willd.) J.P.Roux

Ahamada H. Saïd, Sabine Hennequin, Germinal Rouhan & Jean-Yves Dubuisson, 2017, Disentangling the diversity and taxonomy of Hymenophyllaceae (Hymenophyllales, Polypodiidae) in the Comoros, European Journal of Taxonomy 313, pp. 1-53 : 17

Didymoglossum erosum (Willd.) J.P.Roux

Didymoglossum erosum (Willd.) J.P.Roux , Strelitzia 22: 212 (2008). – Trichomanes erosum Willd. , Species plantarum: 501 (1810). – Type: ‘Habitat in Oware et Benin’, A.M.F.J. Palisot de Beauvois s.n. (holo-: BW20189010!; iso-: P00064998!).

Microgonium erosum (Willd.) C.Presl, Abhandlungen der Königlichen Böhmischen Gesellschaft der Wissenschaften : 335 (1848).

Trichomanes erosum Willd. var. laciniatum Mett. ex Peter, Feddes Repertorium, Beiheft 40 (1): 12 (1929). – Type: ‘Comoren: Ins. Johanna’, s.d., s. coll. s.n. (not located); ‘DOAfr., Ousambara’, s.d., A. Peter 3339 (not located).

Trichomanes aerugineum Bosch, Nederlandsch Kruidkundig Archief 5: 201 (1861). – Type: Fernando Po, C. Barter s.n. (holo-: K000435654!; iso-: K000435653!).

Trichomanes erosum (Willd.) var. aerugineum Bonap. , Notes ptéridologiques 13: 165 (1921).

Microgonium aerugineum (Bosch) Pic.Serm. , Webbia 23: 181 (1968).

Trichomanes palmicola Bosch ex Goddijn, Mededeelingen van ’s Rijks­Herbarium 17: 32, fig. 19 (1913). – Type: Nigeria, C. Barter 2079 (lecto-: L; isolecto-: K000435655!, designated by Pichi Sermolli 1982).

Trichomanes hookeri Bonap. var. cordifolium (Fée) Bonap. , Notes ptéridologiques 10: 30 (1920b), non C.Presl (1843: 16).

Short description

Epiphytic; long-creeping filiform rhizomes, rootless and densely covered by dense black trichomes, bearing widely separated pending fronds; fronds subsessile to well stipitate, up to 1.5 cm long (in Comoros, longer in Continental Africa), ovate or obovate to elliptic, entire to lobed, with palmate venation, and false veins parallel to true veins in addition to a submarginal false vein; sori few, epitactic, campanulate with a slightly dilated mouth.

Global distribution

Comoros, Madagascar, Tropical Africa.

Distribution in Comoros

Anjouan, Mayotte, Mohéli.

Additional specimens examined

COMOROS: ANJOUAN, s. loc., 1850, L.H.Boivin s.n. (P00139625, P00139626). MAYOTTE, s. loc., 1882, E.Marie s.n. (P00139627); Massif du Bénara, crête entre les 2 sommets, 23 Feb. 2015, G.Rouhan et al. 1470 (P02439036), G.Rouhan et al. 1471 (P02439037). MOHÉLI, Chalet Saint Antoine, 5 Nov. 2008, M.Pignal et al. 3484 (P00684897); Piste de Ouala à Fomboni, 28 Mar. 2011, G.Viscardi et al. 419 (P02439809).

Note

Didymoglossum erosum is one out of the two smallest Hymenophyllaceae species in the archipelago with D. rotundifolium . The lamina length exceeds 1.2 cm long and is slightly larger than observed in D. rotundifolium (see here-after), at least for specimens of the western Indian Ocean because continental African specimens (especially in Western Africa) can reach 3–4 cm long. Fronds are also subsessile to well stipitate, entire to lobed, ovate, obovate or elliptic. Confusion can easily be made with small fertile D. cuspidatum (unknown in the archipelago) exhibiting equivalent lamina shape. However, in D. erosum , sori are mostly and clearly well immersed into frond lamina, while in D. cuspidatum each sorus appears quite often well included into a distinct small winged lobe.