Based on the genus Oleandra Cav., from the resemblance of the shrubby upright masses of rhizome branches bearing more or less whorled set of fronds, encountered in some Oleandra species, to the branches of Oleander Nerium oleander.

Oleandra Cav.

Terrestrial, lithophytic or epiphytic homosporous ferns. Rhizome short- to long-creeping, sometimes erect, often much branched, with a dictyostele, scaly; scales peltate, elongate, tapering, with marginal and superficial hairs. Roots arising from ventral side of creeping rhizomes; often unbranched proximally. Fronds simple, entire, monomorphic or dimorphic (not in Australia), often with non-peltate scales on the costa or occasionally on lamina, often with acicular or capitate hairs on veins; venation forked, free or with occasional irregular anastomoses; hydathodes at vein endings. Stipes spread along the rhizome or clustered and whorl-like, arising from all sides of rhizome or dorsally only when creeping, with an articulation point. Sori in one row on each side of the costa; indusia reinform or round, glabrous or hairy. Spores monolete, reinform or ellipsoid, usually with echinate wing-like folds, lacking chlorophyll.

The combination of articulate stipes, simple fronds and indusiate and round or reniform sori is unique to Oleandraceae.

Diploid with n = 41 (Walker 1966, Lӧve et al. 1977). A tetraploid was reported by Manton & Sledge (1954).

Native.

One pantropical genus of 15 species with one species occurring in northeastern Queensland.

Oleandra has previously been included in the family Davalliaceae (e.g. Bell 1998). Phylogenetic analyses of chloroplast DNA sequence data show that Polypodiaceae is closer related to Davalliaceae than Oleandra (Zhang & Zhang 2015), supporting its recognition as a distinct family. Kramer (1990) also included Arthropteris in Oleandraceae based on their shared articulate stipes. However, Arthropteris has been shown to be more closely related to the Tectariaceae (Zhang et al. 2016).

The genus Oleandra and the family Oleandraceae is clearly defined based on its unique and distinctive morphology. In contrast, species delimitation has been fraught with difficulty and the number of species recognised within the genus has varied from as many as 50 (Pichi Sermolli 1965) or 40 (Kramer 1990, Smith et al. 2006) to much more conservative numbers around 15 suggested by regional revisions (Tryon 1997, Hovenkamp & Ho 2012).

Bell, G.H. (1998). Davalliaceae, in McCarthy, P.M. (ed.), Flora of Australia 48: 434–450. (ABRS/CSIRO: Australia).

Hovenkamp, P.H. & Ho, B.-C. (2012). A revision of the fern genus Oleandra (Oleandraceae) in Asia. Phytokeys 11: 1–37.

Kramer, K.U. (1990). Oleandraceae, in Kubitzki, K. (ed.), The Families and Genera of Vascular Plants. Vol. 1 Pteridophytes and Gymnosperms (Vol. eds Kramer, K.U. & Green, P.S.), pp. 190–193. (Springer-Verlag: Berlin).

Lӧve, A., Löve, D. & Pichi Sermolli, R.E.G. (1977). Cytotaxonomical atlas of the Pteridophyta. (J. Cramer: Vaduz).

Manton, I. & Sledge, W.A. (1954). Observations on the cytology and taxonomy of the pteridophyte flora of Ceylon. Philosophical Transactions of the Royal Society London B 238: 127–185.

Nayar, B.K., Bajpai, N. & Chandra, S. (1968). Contributions to the morphology of the fern genus Oleandra. Botanical Journal of the Linnean Society 60: 265–282.

Pichi Sermolli R.E.G. (1965). Adumbratio Florae Aethiopae. 11. Oleandraceae. Webbia 20: 745–769.

PPG I: Schuettpelz, E., Schneider, H., Smith, A.R., Hovenkamp, P., Prado, J., Rouhan, G., Salino, A., Sundue, M., Almeida, T.E., Parris, B., Sessa, E.B., Field, A.R., de Gasper, A.L., Rothfels, C.J., Windham, M.D., Lehnert, M., Dauphin, B., Ebihara, A., Lehtonen, S., Schwartsburd, P.B., Metzgar, J., Zhang, L-B., Kuo, L-Y., Brownsey, P.J., Kato, M. & Arana, M.D. (2016). A community-derived classification for extant lycophytes and ferns. Journal of Systematics and Evolution 54: 563–603.

Smith A.R., Pryer, K.M., Schuettpelz, E., Korall, P., Schneider, H. & Wolf, P.G. (2006). A classification for extant ferns. Taxon 55: 705–731.

Tryon, R. (1997). Systematic notes on Oleandra. Rhodora 99: 335–343.

Tryon, R. (2000). Systematic notes on the Old World fern genus Oleandra. Rhodora 102, 428–438.

Tryon, R.M. & Tryon, A.F. (1982). Tribe Oleandreae, in Ferns and Allied Plants, with Special Reference to Tropical America, pp. 590–599. (Springer-Verlag: New York).

Zhang, L., Schuettpelz, E., Rothfels, C.J., Zhou, X.-M., Gao, X.-F. & Zhang, L.-B. (2016). Circumscription and phylogeny of the fern family Tectariaceae based on plastid and nuclear markers, with the description of two new genera: Draconopteris and Malaifilix (Tectariaceae). Taxon 65: 723–738.

Zhang, L.-B. & Zhang, L. (2015). Didymochlaenaceae: A new fern family of Eupolypods I (Polypodiales). Taxon 64: 27–38.

Walker, T.G. (1966). A cytotaxonomic survey of the pteridophytes of Jamaica. Transactions of the Royal Society of Edinburgh 66: 169–237.

Wheeler, J.R. (1992). Oleandraceae, in Wheeler, J.R. (ed.) et al., Flora of the Kimberley Region, pp. 45–47. (Department of Conservation and Land Management: Como, W.A.).

Published 8 May 2019.