Oleandra wallichii (Hook.) C. Presl, 1836

Hovenkamp, Peter H. & Ho, Boon-Chuan, 2012, A revision of the fern genus Oleandra (Oleandraceae) in Asia, PhytoKeys 11, pp. 1-37 : 19

8. Oleandra wallichii Map 2

Oleandra wallichii C.Presl, Tent. Pterid.: 78. 1836. Fée, Mém. Foug., 5. Gen. Filic.: 304. 1852. Hook., Sp. Fil.: 158. 1862. Ching, Fl. Reipubl. Popularis Sin. 2: 321. 1959. Shieh, DeVol & Kuo in Huang, Fl. Taiwan, ed. 2.: 203, Pl. 83. 1994. X.C.Zhang, Ching Mem. Vol.: 94. 1999. R.M.Tryon, Rhodora 102: 434, fig. 5. 2001. Aspidium wallichii Hook., Exot. Fl.: Pl. 5. 1823. Pl. Neuronia asplenioides D.Don, Prodr. Fl. Nepal.: 7. 1825., nom. illeg. Type: NEPAL.Wallich s.n. (holotype K; isotypes: BM, PE).

Oleandra wallichii var. lepidota Christ, Bull. Acad. Int. Geogr. Bot. 15: 140. 1906. Type: CHINA. Western China: Wilson 5246 (holotype P; isotype: K).

Description.

Rhizome creeping, 3-4 mm thick (2-3 when dry), white waxy in the older parts, with long, leafless parts alternating with more or less dense clusters of very short phyllopodia, usually less than 2 (-5) mm high, of which usually only 1-2 bear fronds at the same time, branches usually in opposite pairs; in cross-section with weak sclerenchyma sheath and without sclerified strands, roots scattered, usually with long unbranched parts. Scales persistently covering the rhizome, peltate, 3-7 × 1-1.3 (-1.5) mm, base appressed, with dark center and lighter margin, acumen brown, usually recurved, with ciliate margin, apex twisted and with frizzly cilia. Fronds monomorphic; stipe 1-5 cm long, with dark coloration on abaxial side often distinctly bicolorous, with catenate hairs; lamina 13-45 × 2-4.5 cm, base truncate to rounded, apex often abruptly caudate, texture thin-herbaceous, translucent, both surfaces densely set with catenate hairs 0.5-1 mm long; costa on lower surface in basal half of lamina with dark coloration, with copious 2-4 mm long pale scales. Sori close to costa, indusium thin, to 1 mm wide, glabrous or hairy. Sporangial stalk without glands below the sporangium. Spores echinate and ridged, perispore solid.

Distribution.

Himalayas to Northern Thailand, Yunnan and Taiwan, 1600 to 3600 m. India, Nepal, Bhutan, China (Yunnan, Taiwan), Thailand.

Ecology.

Mostly epiphytic, on mossy trunks, also on cliff faces or boulders.

Discussion.

Oleandra wallichii differs from Oleandra undulata in the more wide-creeping rhizome that is often distinctly glaucous beneath and between the scales, without sclerenchyma strands; the often conspicuously bicolorous stipe, lamina with usually very distinctly apiculate apex and costa with frequent scales, sori constantly closely costal, with small indusia.

Figures

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