Polystichum pauciaculeatum Bonap.

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 : 279-282

6. Polystichum pauciaculeatum Bonap.

Notes Ptérid. 7: 206 (1918). — Type: d’Alleizette

30, Madagascar, Mandraka (holo-, P!).

Polystichum coursii Tardieu, Mém. Inst. Sci. Madagascar, sér. B, Biol. Vég. 7: 42 (1956) ; Tardieu , in Humbert, Fl. Madag. , fam. 5: 324 (1958). — Type: Cours 4225, Madagascar, Bemainty à Androndramanitra (holo-, P!).

Plants terrestrial. Rhizome short, erect to suberect, to 15 mm in diameter, beset with roots, closely spaced persistent stipe bases, and paleae, the paleae ferrugineous to castaneous, chartaceous. Fronds caespitose, to 9 per plant, suberect to arching, to 1.19 m long; stipe proximally castaneous, distally stramineous, adaxially sulcate, to 615 mm long, to 5 mm in diameter, sparsely to densely paleated, the paleae at the stipe base ferrugineous, chartaceous, broadly attached, narrowly linear, often somewhat rugose, cordate, the margins with short, widely spaced outgrowths (rarely also with unicellular glandular cells), the apex terminates in an acicular cell or small thinwalled cell, to 40 × 3 mm, the paleae higher up the stipe appear heteromorphous, ferrugineous to castaneous, chartaceous, the larger paleae broadly attached, ovate to lanceolate, cordate to cordateimbricate, the margins proximally fimbriate, entire towards the apex, the fimbriae short or long, straight or curved, and simple or branched, the apices usually forked, the paleae apices often flagelliform, terminating in a small thin-walled cell or an acicular cell, to 25 × 6 mm, the smaller paleae short-stalked, hastate, cordate to cordateimbricate, with numerous long marginal outgrowths proximally, the apex entire, subulate, always terminating in an acicular cell; lamina 2-pinnate to 3-pinnate, with up to 28 pairs of stalked pinnae, narrowly ovate to narrowly elliptic, to 685 mm long, bearing 1-5 ferrugineously paleated proliferous buds along the rachis near the apex, the pinnae opposite to alternate, closely to widely spaced, proximal pinnae slightly to strongly reduced, often somewhat deflexed; rachis stramineous, adaxially sulcate, often somewhat flexuose towards the apex, sparsely to densely paleated, the paleae ferrugineous, chartaceous, short-stalked, lanceolate to subulate, cordate to cordate-imbricate, the margins proximally fimbri- ate, entire towards the apex in larger paleae, the fimbriae restricted to the proximal part in smaller paleae, the fimbriae short or long, straight or curved and simple or branched, the apices often forked, the apex usually entire, flagelliform or acicular, often terminating in a small thin-walled cell, to 8 × 2 mm; pinnae 1-pinnate to 2-pinnate, with up to 18 pairs of stalked pinnules, oblong-attenuate, proximally often slightly auriculate acroscopically, to 180 × 33 mm; pinna-rachis stramineous, adaxially sulcate, sparsely to densely paleated, the paleae ferrugineous, chartaceous, narrowly ovate to subulate, short-stalked, cordate to cordate-imbricate, the margins fimbriate, the fimbriae similar to those of the paleae on the stipe and rachis, the apex entire, flagelliform or acicular, usually terminating in an acicular cell (rarely terminating in a small thin-walled cell), to 4.5 × 1 mm; pinnules opposite to alternate, closely to widely spaced, proximally short-stalked, sessile towards the apex, firmly herbaceous, dark green adaxially, slightly paler abaxially, inaequilateral, broadly ovate to rhombic, basiscopically cuneate, acroscopically truncate and auriculate, the larger pinnules commonly deeply incised at the base and thus forming a nearly free auricle, the margins serrate, aristate, to 27 mm long, adaxially sparsely beset with twisted stramineous paleae chiefly along the costa, subulate or proximally with one or more short or long marginal outgrowths, the apical cell is always acicular, to 4 mm long, abaxially moderately paleated, the paleae stramineous, membranous, short-stalked, subulate to narrowly triangular, proximally with a few short or long, simple or branched marginal outgrowths, the apex always terminates in an acicular cell, to 2.2 mm long. Venation evident or obscure. Sori circular, to 1.5 mm in diameter, terminal or near-terminal, essentially uniseriate, discrete to slightly confluent at maturity; sporangium with 11(-13-)30-indurated annulus cells; indusium stramineous, persistent, circular to amorphous, usually simple but often with a small or large wing, repand to erose, maximum radius 0.43(-0.64-) 0.9 mm; spores castaneous, the perispore folded to form inflated tubercules and ridges, echinulate to verruculate, closely perforated, exospore 30(-37.89-)48 × 20(-27.06-)44 µm. Chromosome number unknown. — Figs. 5, 6D-F.

MATERIAL EXAMINED. — MADAGASCAR: Baron 2161, without precise locality ( P); Benoist 986, Ankaratra, Manjakatompo ( P); Bosser 10985, Ankaratra (Manjakatompo), 2000 m ( P); Capuron 4, Angavokely ( P); Cours 4225, Bemainty à Androndramanitra, 800-850 m ( P); d’Alleizette 30, 84, Mandraka ( P); Decary 13363, Manjakatompo ( P); Decary 17542, forêts au sud d’Ambositra ( P); Hildebrandt 3766, Ost-Imerina: Andrangaloaka ( B [4 sheets], K, P); Hodgkin & Stanfield s.n., Central Plateau, ( K [3 sheets]); Humbert 3243, Pic d’Ivohibe (Bara), 1500-2000 m ( P); Humbert 3730, massif de l’Andringitra (Iratsy): vallées de la Riambava et de l’Antsiforta et montagnes environnantes, 2000 m ( P); Humbert 6096, massif de l’Andohahelo: vallée de Ranohela, 1200-1800 m ( P); Humbert 11121, Tampokesta au N d’Ankazobe: forêt d’Ambohitantely, 1600 m ( P); Humbert & Capuron 28402, environs d’Ambatofinandrahana (Betsileo) au km 300 de la route Tananarive-Fianarantsoa, 1550-1600 m ( BOL, BR, L, P [2 sheets]); Humbert & Capuron 30273, massif de l’Ankaratra, forêt de Manjakatompo, 1700- 2200 m ( P); Leandri et al. 3396, massif de l’Andringitra: forêts de Imaiso, 1500-2000 m ( P); Onraedt 10 M 87, Ambatofitorahana, 35 km au sud d’Ambositra, 1600 m ( BR); Perrier de la Bâthie 7928, massif de l’Andringitra, 2000-2400 m ( P); Perrier de la Bâthie 13362, Mt. Tsiafajavona (Ankaratra), 2000- 2400 m ( P); Pool s.n., Antananarivo ( K); Raharijaona s.n., recueillies dans la forêt d’Ankeramadinika (district de Manjakandriana, 1300 m ( P); Ramuarya 1871, forest near Ankerameduika ( K); Rauh 7669, wald 30 km südlich Ambositra ( M); Viguier & Humbert 1699 , province du Vakinankaratra, district d’Ambatolampy, Est d’Ankaratra, du Tsiafajavona, 1800-1900 m ( P); Waterlot 834, Angavo, Tananarive ( P); Herb. Jard. Bot. Tananarive 4761, Forêts du Tritondroina, 1800 m ( P); sine coll. s.n., Mandraka (Herb. PIC. SERM. 15765).

Polystichum pauciaculeatum was first collected by D’ ALLEIZETTE in December 1905, but was not formally described until 1918 by BONAPARTE who suggested that it belonged to the P. aculeatum group. TARDIEU- BLOT (1956a, 1956b), in her treatment of the Madagascan Polystichum species , and later also in the flora of Madagascar and the Comores (1958), makes no reference of this species. Polystichum coursii , here considered synonymous with P. pauciaculeatum , was suggested to belong to the P. setiferum group of species (TARDIEU 1956b). Several collections belonging to this species were cited as belonging to P. pungens (Kaulf.) C. Presl by CHRISTENSEN (1932). Polystichum pungens is, however, confined to South Africa ( ROUX 2000).

BONAPARTE (1918), in describing P. pauciaculeatum , does not mention that the species is proliferous. The type specimen does, however, posses poorly developed buds that are easily overlooked. Similarly, the type of P. coursii also has poorly developed proliferous buds.

DIAGNOSTIC FEATURES AND RELATIONSHIPS. — Considering palea morphology, Polystichum pauciaculeatum is related to P. kilimanjaricum and P. tsaratananense . It can, however, be separated from these species by the usually ferrugineous, somewhat rugose, very long and narrow stipe base paleae and the firmly textured, often castaneous, ovate to lanceolate paleae with closely but shortly fimbriated margins that extend to the rachis. Polystichum pauciaculeatum belongs to section Metapolystichum Tagawa.

VARIATION. — Polystichum pauciaculeatum shows extreme variation in a large number of features. Perhaps the most apparent is the frond architecture and paleae density. Stipe length ranges from 90 to 612 mm, whereas the lamina length varies between 370 and 685 mm. The proximal pinnae in some plants are widely spaced and hardly reduced whereas in others they are strongly reduced, resulting in a narrowly elliptic lamina outline. Pinnules also vary significantly in size and division. In some plants the proximal acroscopic pinnules are divided near the base to form an almost free auricle, but in others both the acroscopic and basiscopic pinnules are divided to the base forming free, broadly ovate to rhombic segments.

Variation in palea density is especially striking. Some plants are sparsely paleated whereas others are densely beset with stramineous to ferrugineous paleae along the stipe, rachis and pinnarachises. The morphology of the paleae, however, shows little variation. The larger paleae along the rachis are generally stramineous to ferrugineous, but in some plants they are centrally castaneous.

The number of proliferous buds along the rachis also varies significantly. Although only one or two buds per frond are generally well developed (rarely up to five), there are many more, but these are usually undeveloped and easily overlooked.

DISTRIBUTION AND ECOLOGY — Polystichum pauciaculeatum is endemic to Madagascar and confined to the central highlands. The species is adapted to a wide range of habitats and occurs at elevations ranging from 800 to 2400 m. It is largely a forest species occurring in lowland rain forests, moist montane forests and montane bushland and thickets. On Mount Ankaratra it grows in volcanic-derived soils whereas to the south, on Mt. Andringitra, it grows in soils of granitic origin.