Oleandra undulata (Willd.) Ching, 1933

Hovenkamp, Peter H. & Ho, Boon-Chuan, 2012, A revision of the fern genus Oleandra (Oleandraceae) in Asia, PhytoKeys 11, pp. 1-37 : 17-18

6. Oleandra undulata Map 2

Oleandra undulata Ching, Lingnan Sci. J. 12: 565. 1933. Holttum, Rev. Fl. Mal. 2: 384. 1954. Ching, Fl. Reipubl. Popularis Sin. 2: 322. 1959. X.C.Zhang, Ching Mem. Vol.: 92. 1999. R.M.Tryon, Rhodora 102: 346, fig. 6. 2001. Polypodium undulatum Willd., Sp. Pl., ed. 4 [Willdenow] 5: 155. 1810. Type: INDIA. Tranquebar: Klein 887 (holotype: B - Willdenow 19616 -01 0).

Oleandra pubescens Copel., Univ. Calif. Publ. Bot. 12: 397, Pl. 52A. 1931. Type: THAILAND. Eryl Smith 1072 (holotype: UC*).

Description.

Rhizome short-creeping, little branching, 5-6 mm thick (3-5 when dry), not white waxy, in cross-section with many scattered sclerified strands; phyllopodia irregularly scattered, close together or distant, 2-8 cm long, roots scattered, without distinct unbranched parts. Scales persistently covering the rhizome, peltate, 3-5 × 1-1.6 mm, slightly spreading, acumen brown, with sparsely ciliate margin, apex short, wide. Fronds monomorphic; stipe 3-15 cm long, without dark coloration, articulation at 1 /5-1/2 from base; lamina to 60 × 1-5.5 cm, widest in middle part, base truncate or cuneate to gradually narrowed, apex acute to narrow-acuminate, texture herbaceous, upper surface glabrous or sparsely, lower surface more densely set with usually acicular, sometimes slightly catenate hairs to c. 0.5-1.0 mm long; costa on lower surface without dark coloration, without scales. Sori close to costa or leaving a distinct 1-6 mm wide sterile zone between costa and soral zone, indusium firm, to 2 mm wide, hairy. Sporangial stalk without glands below the sporangium. Spores finely papillose and coarsely ridged, perispore baculate, outer layer not perforated.

Distribution.

Burma, Laos, Thailand, China: Yunnan. Mostly below 1000 m.

Ecology.

In open or deciduous forests, often disturbed; terrestrial or epilithic, rhizome subterraneous, on rocks or in crevices, mostly on granite.

Discussion.

Oleandra undulata can be difficult to distinguish from Oleandra cumingii . In addition to the differences listed under that species, subterraneous growth of the rhizome may be characteristic for Oleandra undulata , but field observations are lacking for many specimens.

Figures

Map 2. Distribution of Oleandra cumingii (squares), Oleandra undulata (triangles), Oleandra wallichii (circles).