Polystichum tsaratananense Tardieu

Roux, Jacobus P., 2001, A review of the fern genus Polystichum (Pteropsida: Dryopteridaceae) in Madagascar and the Mascarene region, Adansonia (3) 23 (2), pp. 265-287 : 282-284

7. Polystichum tsaratananense Tardieu

Mém. Inst. Sci. Madagascar, sér. B, Biol. Vég. 7: 44 (1956); in Humbert, Fl. Madag. , fam. 5: 322 (1958). — Type: Humbert 18144, Madagascar, massif du Tsaratanana, montagnes entre le haut Sambirano et le haut Maivarano (entre Mangindrano et Ampanompia), 1400-1800 m. Forêt ombrophile sur latérite de gneiss (holo-, P!).

Plants terrestrial. Rhizome short, erect to suberect, to 10 mm in diameter, densely beset with roots, closely spaced persistent stipe bases, and paleae, the paleae ferrugineous, dark brown or ebeneous with narrow pale brown margins, nitid, chartaceous to crustaceous, broadly attached, narrowly linear-attenuate to narrowly lanceolate, cordate, the margins beset with widely spaced, short, apically or basally directed outgrowths, the apex terminates in a long acicular cell, to 20 × 0.3 mm. Fronds caespitose, suberect to arching, to 1.1 m long; stipe proximally castaneous, stramineous higher up, sulcate adaxially, to 370 mm long, to 6 mm in diameter, densely beset with paleae appearing heteromorphous, the larger paleae ferrugineous and chartaceous throughout or crustaceous, nitid, and black to dark brown with a narrow pale brown margin, broadly attached, cordate, the margins closely beset with short simple or branched, straight or curved outgrowths, the apex terminates in an acicular cell, to 25 × 4 mm, the smaller paleae ferrugineous to stramineous, chartaceous, sessile or short-stalked, ovate to narrowly triangular, cordate to cordate-imbricate, the margins closely beset with simple or branched, short or long, straight or curved out- growths that become more widely spaced distally, the apex terminates in an acicular cell or rarely in a small oblong thin-walled cell; lamina 2-pinnate to 3-pinnate, with up to 27 pairs of stalked pinnae, ovate-lanceolate, often with a paleated proliferous bud abaxially in a distal pinna axil, to 800 mm long, the proximal pair not or slightly reduced, somewhat deflexed; rachis stramineous, sulcate adaxially, densely paleated, the paleae ferrugineous to stramineous, chartaceous, short-stalked, narrowly ovate, ovatelanceolate, oblong-attenuate or subulate, cordate to cordate-imbricate, the margins closely beset with short or long, simple or branched, straight or curved outgrowths, entire towards the apex in smaller paleae, terminating in an acicular cell, to 10 × 2 mm; pinnae 1-pinnate, with up to 13 pairs of stalked pinnules, broadly to narrowly oblong-attenuate, opposite to alternate, shortstalked, widely spaced or slightly imbricate, firmly herbaceous, to 190 × 50 mm, the proximal acroscopic pinnule usually longer than the next; pinna-rachis stramineous, sulcate adaxially, closely paleated, the paleae ferrugineous to stramineous, chartaceous, short-stalked, narrowly lanceolate, narrowly oblong or subulate, cordate to cordate-imbricate, proximally closely beset with long and short, simple or branched, usually twisted outgrowths, entire towards the apex, the apex terminates in an acicular cell, to 6 × 1 mm, rarely also bearing paleated proliferous buds near the pinna apex; pinnules opposite to alternate, proximally short-stalked, sessile distally, imbricate or not, inaequilateral, ovate, obliquely rhomboid or falcate, basiscopically narrowly cuneate, acroscopically cuneate to truncate and auriculate, the larger pinnules lobateserrate, the smaller pinnules serrate to doubly serrate, aristate, to 35 mm long, adaxially sparsely beset with simple filiform paleae terminating in an acicular cell, to 2.8 mm long, abaxially sparsely set with stramineous, short-stalked, filiform to subulate paleae with a few straight and simple or branched marginal outgrowths, the apex terminates in an acicular cell, to 2.5 mm long. Sori circular, to 1.5 mm in diameter; sporangium with 12(-14-)16- indurated annulus cells; indusium stramineous, subentire, maximum radius 0.34(-0.42-) 0.53 mm; spores unknown. Chromosome number unknown. — Fig. 6 G-J.

MATERIAL EXAMINED. — MADAGASCAR: Humbert 18144, montagnes entre le haut Sambirano et le haut Mairarano, 1400-1800 m ( P); Humbert 18475, massif du Tsaratanana, plateau supérieur et hauts sommets de l’Amboabory à l’Antsianongatalata, 2000-2700 m ( P); Humbert 18266, massif du Tsaratanana et haute vallée du Sambirano, ± 2000 m ( P [2 sheets]); Perrier de la Bâthie 7642, massif de Manangarivo, 1200 m ( P [2 sheets]); Humbert & Capuron 25035, montagnes au nord de Mangindrano (haute Maevarano), jusqu’au sommet d’Ambohimirahavavy, 1900 m ( L, P [3 sheets]); Rauh s.n., Mandraka-Schlucht ( M).

DIAGNOSTIC FEATURES AND RELATIONSHIPS. — Polystichum tsaratananense is characterized by the narrow, crustaceous, dark brown to black stipe paleae. Although the stipe paleae in some plants are ferrugineous to stramineous, at least some paleae at the stipe base are usually densely impregnated. The short, curved, marginal outgrowths of the paleae and the small, subentire to repand indusia are also diagnostic.

Based on palea morphology, P. tsaratananense appears to have a closer affinity with P. kilimanjaricum Pic. Serm. from Africa than with any of the Mascarenes species. Both taxa are characterized by the presence of proliferous buds near the frond apex. In P. tsaratananense the rhizome and stipe paleae are generally densely impregnated but are narrower and much longer than in P. kilimanjaricum . The paleae in both species terminate mostly in an acicular cell; in P. tsaratananense the outgrowths are short and curved whereas in P. kilimanjaricum they are long, slender and relatively straight. The indusia of P. tsaratananense are also smaller (0.34(-0.42-)0.53) than those of P. kilimanjaricum (0.73(-0.87-)1.02). Polystichum tsaratananense belongs to section Lasiopolystichum Daigobo.

VARIATION. — The degree to which the paleae of the stipe are impregnated shows the highest degree of variation. In some plants only a few paleae at the stipe base are impregnated whereas in others impregnated paleae may extend to the lamina base. Tripinnate fronds in this essentially 2-pinnate species are known but not very common.

mm 0.5

DISTRIBUTION AND ECOLOGY. — Polystichum tsaratananense is endemic to Madagascar, where it is confined to the northern part of the central highlands. It is a forest species and essentially con-

fined to elevations between 1200 and 2700 m. At lower elevations the species occurs on gneiss or silicaceous soils but on Mount Tsaratanana above 2000 m the soils are basalt-derived.

Figures

Fig. 6. — Stipe and lamina paleae in Polystichum species.— Polystichum maevaranense: A, rachis palea; B, proliferous bud palea; C, apex of B showing the cellular structure. Humbert 15019 (P). — Polystichum pauciaculeatum: D, stipe palea. Leandri et al. s.n. (P); E, margin of D showing the cellular structure; F, lamina palea, abaxial surface. Humbert 11121 (P). — Polystichum tsaratananense: G, stipe palea; H, apex of G showing the cellular structure. Humbert & Capuron 25035 (P); I, lamina palea (abaxial surface); J, apex of I showing the cellular structure. Humbert 18144 (P). — Polystichum wilsonii: K, stipe palea; L-M, lamina palea, abaxial surface. K-L, Alluaud 241 (P); M, Esterhuysen 26699 (BOL).