Dicksonia ceramica Lehnert, 2018

Lehnert, M. & Coritico, F. P., 2018, The genus Dicksonia (Dicksoniaceae - Cyatheales) in western Malesia, Blumea 63 (1), pp. 268-278 : 275-276

4. Dicksonia ceramica Lehnert , sp. nov. — Fig. 5 ; Map 1

A species with only soft, woolly hairs, Dicksonia ceramica differs from D. lanigera from New Guinea in shedding most of the hairs on the abaxial surfaces of the rachis, costae and costules, exposing the shiny atropurpureous to blackish epidermis (vs hairs mostly persisting, epidermis dull brown, not shiny). — Type: Kato, Ueda & Mahjar C-1340 (holo K-000548897/- 000548898;iso BO? n.v., L-1258681,TO n.v.), Indonesia,Seram, Manusela National Park,along trail between Hatuemete (seaside) and Maraina (810 m) in Manusela Valley via Hoale Pass (1770 m) in Murkele Ridge, Kecamatan (District) Tehoru and Seram Utara, S03°10 –14' E129°35 –37', 18 Nov. 1983.

Etymology. Named after the type locality (Latin ceramicus = from Seram).

Tree fern, terrestrial. Trunks to 4 m tall, otherwise unknown; adventitious buds not reported. Fronds to 200 cm long. Petioles to 30 cm long (to 40 cm in sterile fronds), c. 1/6 of frond length, densely covered with reddish brown ciliform hairs to 4 cm long, mostly spreading but soft and often appressed, with undercoat of spreading pale, catenate hairs with dark brown acicular tips, 1–2 mm long; hairs if abraded leaving a smooth to faintly scabrous surface. Laminae to 170 by 80 cm, tripinnate-pinnatifid, coriaceous, shape unknown, weakly dimorphic with fertile parts more deeply dissected, occurring throughout the lamina. Leaf axes (rachises, costae and costules) shiny, dark castaneous to atropurpureous, appearing blackish in most parts, including most parts of costules, smooth to faintly scabrous, adaxially with antrorsely curved hairs to 1.5 mm long, pale reddish brown to whitish, persistent but relatively sparse, abaxially probably first covered with similar but generally shorter hairy indument as on the petioles but soon glabrescent, remnants of longer turgid brown hairs to 15 mm long and much shorter undercoat hairs persist in axils, costules distally with some persisting turgid spreading hairs to 1.5 mm long, pale brown with whitish tips. Pinnae to 40 by 16 cm, subsessile to stalked 1 cm, lanceolate with attenuate tips and ± truncate bases, the basal pinnule pair may be covering the rachis adaxially; c. 8–10 pinna pairs per frond, most pinnae patent, basal pinna pairs c. 1/4 the length of longest pinnae, not reflexed. Largest pinnules (sterile ≈ fertile) to 9.5 by 2.5 cm, lanceolate, subsessile to short-stalked to 1 mm, ± 2 cm between costules with ± truncate bases and attenuate apices. Sterile segments to c. 13 by 5 mm, sessile, free to adnate, oblong, most weakly oblique, straight or distally curved, margins crenate to lobed, the tips obtuse to acute, separated by narrow sinuses to 1 mm wide; fertile segments to 13.0 by 4.5 mm, approximate, sessile, free to adnate, deeply lobed but laminar tissue not reduced to narrow strands along the veins, most lobes with simple veins, only few basal lobes with one sorus on acroscopic fork of a vein, subtended by a sterile lobe not reaching beyond the sorus; segment tips a coarsely serrate sterile lobe. Veins mostly glabrous except for persisting turgid spreading hairs to 1.5 mm long, pale brown with whitish tips on midveins adaxially. Sori 1.6–2.0 mm wide, slightly kidney-shaped when closed, circular when open; indusia bivalved, outer one pale brown with paler cartilaginous margin, inner one light brown with slightly erose margins, somewhat darkened; paraphyses longer than sporangia, thin, pale tortuous, fragile. Spores tetrahedral-globose, whitish to pale yellow, exospore areolate with weakly protruding ridges, presumably covered in papillate-granulate to baculate perispore (only light microscopic evidence), forming a retate pattern (‘verrucose’ sensu Holttum 1963).

Distribution — Restricted to the island of Seram, Indonesia.

Habitat & Ecology — At 980–1830 m in mossy montane forests on limestone ( Kato 1990).

Vernacular name — ‘Seram woolly tree fern’, suggested herewith.

Additional specimens (paratypes). INDONESIA, Maluku, Seram, Manusela National Park, along a trail between Hatuemete (sea level) and Hoale Pass (1770 m), southern slope of Murkele Ridge, Kecamatan (District) Tehoru and Seram Utara, S03°13 –16' E129°36 –37', 1770 m, 21 Feb.1985, Kato, Ueda , Okamoto, Akiyama, Sunarno & Mahjar C-7492 (K-000548899, L-1258680); Kecamatan (District), Tehoru, along a trail from Hunisi to Muselleinan Pass (1280 m), S03°12 –14' E129°45 –48', 1280 m, 27 Aug. 1986, Kato, Ueda & Famani C-14048 (BO (image), TI n.v.).

Note — Dicksonia ceramica has been collected several times, and it is the only known species of the genus on Seram ( Kato 1990). On one label, Kato indicated little variation occurring in the species on the island, and so, trusting Kato’s taxonomic expertise, the two collections that we were not able to consult (Kato et al. C-13608 and C-13837, BO, TI) are con- sidered most likely conspecific. Dicksonia ceramica was first determined and reported as D. lanigera based on its soft hairs, and it also resembles the New Guinean species D. hieronymi Brause in frond dissection (but D. hieronymi usually has a small sterile lobe subtending each sorus, whereas D. ceramica lacks this lobe). Unlike the other two mentioned species, D. ceramica loses most of its hair abaxially on the thinner frond axes, re- vealing their dark colour. In D. lanigera , the hairs are usually persisting and if removed the axes are not dark and shiny; in D. hieronymi it is mostly the same, but in some populations the epidermis of the axes may be dark and shiny. These plants of D. hieronymi still differ from in having the epidermis of the axes scabrous with spreading hairs (vs smooth epidermis, matted hairs in D. ceramica ).

Figures

Map 1 Distribution of Dicksonia in western Malesia: D. amorosoana (O), D. blumei (D), D. celebica (Δ), D. ceramica (A), D. mollis () and D. timorensis (z). Map by R. Cámara-Leret.

Fig. 5 Dicksonia ceramica Lehnert. a. Detail of petiole, hairs partially removed in upper part; b. pinnule adaxially; c. fertile segments abaxially (Kato, Ueda & Mahjar C-1340, holo K).