Hymenasplenium unilaterale

Aspleniaceae

Hymenasplenium unilaterale (Lam.) Hayata

Link to Australian Plant Name Index for publication details and synonyms: https://id.biodiversity.org.au/name/apni/211831

Lithophytic ferns with pendent fronds. Rhizome short-creeping, scaly. Stipe and rachis dark red-brown, sparsely scaly, glossy; stipe 8–23 cm long, 0.5–1.5 mm diam. Lamina narrowly triangular or narrowly ovate, pinnate, 12–28 cm long, 4–8 cm wide, pale green, thin, ±glabrous. Pinnae in 14–22 pairs, narrowly oblong, sometimes slightly falcate, inserted at acute angles to rachis; basal, basiscopic portion excised so that each pinna appears to be joined to a short stalk in the lower corner; line of excision at c. 10–30° to midrib; margins serrate; apices acute to acuminate; longest pinnae at c. three-quarters distance to base, 25–45 mm long, 6–10 mm wide, gradually decreasing upwards to the apex; basal pair not deflexed. Sori to 5 mm long.

In Australia known only from Mt Bartle Frere area. Also scattered across Palaeotropics.

Lithophytic or terrestrial on steep rocky walls in shaded high rainfall montane vine forest.

The Australian population may be apogamous (Jones 1998).

Hymenasplenium excisum and Hymenasplenium wildii.

1a.  Pinnae 5–8 pairs, pinnae < than 2.5 cm long, lowland habitat = Hymenasplenium wildii

1b.  Pinnae 9 or more pairs, pinnae > 2.5 cm long, montane habitat = 2.

2a.  Frond apex attenuate, basal pair of pinnae deflexed, lateral pinnae deeply excised = Hymenasplenium excisum

2b. Frond apex not attenuate, basal pair of pinnae not deflexed, lateral pinnae not deeply excised = Hymenasplenium unilaterale