Hymenophyllum hirsutum

Dubuisson, Jean-Yves, Pechon, Timothée Le, Bauret, Lucie, Rouhan, Germinal, Reeb, Catherine, Boucheron-Dubuisson, Elodie, Selosse, Marc-André, Chaussidon, Cécile, Dajoz, Isabelle, Pynee, Kersley, Grangaud, Edmond, Robert, Yannis, Tamon, Jean- Maurice & Hennequin, Sabine, 2018, Disentangling the diversity and taxonomy of Hymenophyllaceae (Hymenophyllales, Polypodiidae) in the Mascarene archipelago, with ecological implications, Phytotaxa 375 (1), pp. 1-58 : 33-34

21. Hymenophyllum hirsutum (L.) Sw. ( Swartz 1800: 99), Fig. 16A–C

Trichomanes hirsutum L. ( Linné 1753: 1098). ≡ Sphaerocionium hirsutum (L.) C.Presl ( Presl 1843: 34). Type:—based on Plumier (see Cremers & Aupic 2008), ‘Plum. fil. 73, t.50, f.B; Pet. fil. 105, t.15, f.5. Habitat in America’ (lectotype: Traité des fougères de l’Amérique (1705), t. 50, fig. B, designated by Morton 1947); Plumier in herbier Tournefort 5315-1 (epitype P-TRF, P00322153!, designated by Cremers & Aupic 2008).

= Trichomanes ciliatum Sw. ( Swartz 1788: 136). ≡ Hymenophyllum ciliatum (Sw.) Sw. ( Swartz 1800: 100). ≡ Sphaerocionium ciliatum (Sw.) C.Presl ( Presl 1843: 34). Type:— JAMAICA. Without locality, without date, O. Swartz s.n. (lectotype S, S-R-2960!, inadvertently designated by Proctor (1985); isolectotypes B, BW 20 222010!, LD, LD1773824!). Note: The combination Hymenophyllum ciliatum (Sw.) Fosberg , coined by Fosberg (in Fosberg & Sachet 1980: 1) and listed as such in some floras and databases, is illegitimate. Fosberg noted he had not found such a combination but he thus omitted the earlier work by Swartz, published in 1800.

= Hymenophyllum arbuscula Desv. ( Desvaux 1827: 332). Type:— LA REUNION. ‘Habitat in Borbonia’, without date, without collector (lectotype P, P00477831!, here designated).

= Hymenophyllum ciliatum (Sw.) Sw. var. imbricatum Bonap. (Bonaparte 1923: 200). Type :— GABON. ‘ Pays Itsogho. Vallée de la Waka. Entre Moubenu et Dizoma.’, October 1916, G. Le Testu 2160 (holotype P, P00483495 !; isotype P, P00483494 !).

= Hymenophyllum boryanum Willd. (Willdenow 1810: 518, 519). ≡ Hymenophyllum ciliatum (Sw.) Sw. var. boryanum (Willd.) Mett. ex Kuhn ( Kuhn 1868: 39). Type :— LA REUNION. ‘ Bourbon’, without date, J.B.G.M. Bory de St.- Vincent s.n. (lectotype B, BW 20 240010!, here designated; isolectotype P, P00477832 !).

Note: Hymenophyllum ciliatum (Sw.) Sw. var. majus Tardieu ( Tardieu-Blot 1951: 14) was previously listed as additional synonym ( Saïd et al. 2017) but our re-examination of specimens (P01315030, P00483494) seems to indicate that they rather belong to the distinct Malagasy H. poolii Baker ( Baker 1876: 415) or eventually are hybrids between H. hirsutum and H. poolii (as also suggested by F. Rakotondrainibe, comm. pers.), hence explaining that we excluded this taxon for this treatment.

Short description—Epiphytic; long-creeping filiform rhizomes, bearing sparsely distributed roots and long reddish-brown trichomes, and widely separated pending fronds; fronds with winged stipes and rachises ( Fig. 16B ), up to 13 cm long, lanceolate to triangular, pinnate-pinnatifid to bipinnate-pinnatifid, densely hairy with light reddish-brown, stellate, pedonculated trichomes on rachises, veins and margins; numerous sori, round, paratactic, bilabiate without a developed base nor lateral veinlets and with hairy margins; receptacle short and included ( Fig. 16C ).

Global distribution—Western Indian Ocean, tropical Africa, Neotropics.

Current distribution in Mascarenes— La Réunion, Mauritius.

Ecology—Epiphytic on tree-trunks in lowland rainforests (150–1,000 m).

Representative specimens examined— MAURITIUS. Pigeon Wood, September 2009, K. Pynee et al. s.n. ( MAU 0011517 ) ; Pétrin , February 2016, K. Pynee et al. s.n. ( MAU 0019002 ) ; Mt Cocotte , October 2010, S. Hennequin et al. 323 ( MAU 0022461 , P02432384 ) .

— LA RÉUNION. Mare Longue, April 2002, J.-Y. Dubuisson HR 2002-16 (P0243298).

Note—This species is easily distinguished from the other hairy Mascarenan Hymenophyllum species by its fully winged stipes.

Figures

FIGURE 16.A. Hymenophyllum hirsutum (L.) Sw., as epiphyte (La Réunion, ‘Grand Etang’). B. H. hirsutum, detail of a frond showing the hairy winged stipe. C. H. hirsutum, detail of bilabiate hairy sori. D. H. hygrometricum (Poir.) Desv., as epiphyte (La Réunion, ‘Bébour’). E. H. hygrometricum, wet fronds become greener as shown here (photographs. A: J.-Y. Dubuisson; B–C: L. Bauret; D–E: C. Chaussidon).