Aspidium stramineum, 2001

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 : 267-271

1. Polystichum ammifolium (Poir.) C. Chr.

Cat. Pl. Madag., Pterid.: 31 (1932); Dansk Bot.

Ark. 7: 69 (1932). — Polypodium ammifolium Poir. , in

Lam., Encycl. 5: 554 (1804). — Aspidium ammifolium

(Poir.) Desv., Ges. Naturf. Freunde Berlin Mag.

Neuesten Entdeck. Gesammten Naturk. 5: 321

(1811); Desv., Mém. Soc. Linn. Paris 6: 250

(1827). — Lectotype (here designated): Commerson

s.n., Isle-de-France ( Mauritius), (P-LA; iso-, BOL,

NBG, photo!).

Aspidium stramineum Kaulf. , in Spreng., Syst. Veg., ed. 16: 105 (1827). — Polystichum stramineum (Kaulf.) C. Presl, Tent. Pterid. : 83 (1836). — Type: Sine coll. s.n., Mauritius [erroneously given as C. B. S. (Caput Bonae Spei)], missing.

Hypopeltis mauritiana Bory , in Bél., Voy. Indes Or.: 67 (1833). — Polystichum mauritianum (Bory) Fée, Mém. Foug. 5: 278 (1852). — Type: Bory de Saint- Vincent s.n., les grands bois de l’île Maurice ( Mauritius), n.v.

Polystichum schizolobium Fée, Mém. Foug. 7: 99 (1857). — Type: De Montbrison s.n., Bourbon ( La Réunion), n.v .

Polystichum vestitum Sieber, Fl. Mauritiana , ed. 1, suppl. n. 48, nom. nud., non (G. Forst.) Sw. (1801).

Polystichum sieberianum C. Presl, Tent. Pterid. : 83 (1836), nom. nud.

Aspidium aculeatum auct.: Baker, Fl. Mauritius: 492 (1877); Cordem., Fl. Réunion: 71 (1895); non (L.) Roth (1799).

Plants terrestrial or epilithic. Rhizome suberect, short, to 140 mm long, to 15 mm in diameter, beset with roots, crowded, persistent stipe bases, and paleae. Fronds crowded, caespitose, up to 16 per plant, erect to suberect or arching, to 1.4 m long; stipe proximally castaneous or stramineous throughout, adaxially sulcate, to 600 mm long, to 8 mm in diameter, densely paleated, the paleae at the stipe base ferrugineous, membranous, sessile or short-stalked, filiform, narrowly linear to narrowly oblong-attenuate, entire or with few widely spaced short marginal outgrowths, the apex terminates in an acicular cell or a small thin-walled cell, to 50 × 2 mm, the paleae higher up appear heteromorphous, the larger paleae concolorous or bicolorous, stramineous or ferrugineous, membranous or centrally castaneous, nitid and crustaceous, sessile, ovateattenuate to narrowly ovate-attenuate, cordate to cordate-imbricate, the margins closely set with short and/or long fimbriae or with short, forked marginal outgrowths which reduce in size and number towards the apex, the apex entire, terminating in a long or short acicular cell, to 15 × 6 mm, the smaller paleae ferrugineous, membranous, sessile or short-stalked, ovate-attenuate to narrowly triangular or subulate, mostly cordateimbricate, the margins proximally with long twisted, simple or branched outgrowths, the apex entire, terminating in an acicular cell; lamina 2- to 3-pinnate, with up to 32 pairs of stalked pinnae, narrowly ovate to ovate-lanceolate, to 790 mm long, pinnae opposite or alternate, closely spaced, proximally often somewhat more widely spaced, the proximal pinnae slightly reduced; rachis stramineous, adaxially sulcate, densely paleated, the paleae appear heteromorphous, stramineous or ferrugineous, membranous to chartaceous, the larger paleae sessile, oblong-attenuate, narrowly ovate-attenuate, narrowly triangular to subulate, the margins closely set with short simple or branched straight or curved marginal outgrowths which reduce in size and number towards the apex, the apex entire, the smaller paleae short-stalked, cordate to cordate-imbricate, the margins usually with a few long simple or branched outgrowths proximally, the apices are always entire, terminating in a long acicular cell or a short subulate cell (rarely also in a short oblong-obtuse thin-walled cell), to 9 × 3 mm; pinnae short-stalked, 1-pinnate to 2-pinnate, with up to 21 pairs of stalked pinnules, oblong-attenuate to narrowly oblong-attenuate, often slightly to strongly auriculate acroscopically, the middle pinnae to 170 mm long, to 62 mm wide; pinna-rachis stramineous, adaxially sulcate, moderately to densely paleated, the paleae ferrugineous, membranous, ovate-attenuate to subulate, the larger paleae sessile, the smaller short-stalked, truncate to cordate-imbricate, the margins proximally closely or widely set with short and/or long, simple or forked marginal outgrowths which reduce in size and number towards the apex, the apex entire, terminating in a long acicular cell (rarely also in a short oblong-obtuse thin-walled cell), to 5 × 1 mm; pinnules opposite or alternate, closely spaced, often slightly imbricate, short-stalked proximally, sessile towards the pinna apex, firmly herbaceous, dark green adaxially, slightly paler abaxially, inae- quilateral, ovate, narrowly ovate, trullate or oblong-attenuate, basiscopically cuneate, acroscopically cuneate to truncate and auriculate, shallowly lobed or deeply incised to form lanceolate , narrowly elliptic, ovate to obovate lobes, the proximal acroscopic auricle free or nearly free, the margins crenate to doubly serrate, pungent or aristate, the proximal acroscopic pinnule to 35 × 14 mm, often reaching beyond the pinna-rachis above, adaxially moderately beset with stramineous to ferrugineous, membranous, shortstalked, subulate to narrowly triangular paleae, the margin proximally with long, simple, largely basally directed marginal outgrowths, the apex always entire and terminating in a long acicular cell, to 1.8 mm long, abaxially moderately set with stramineous to ferrugineous, membranous, short-stalked, subulate to narrowly triangular paleae, proximally with long, simple, largely basally directed marginal outgrowths, the apex always entire, terminating in a short fusiform cell or a long acicular cell (rarely also in a small thinwalled cell), to 2.7 mm long. Venation evident or obscure. Sori circular, to 1.5 mm in diameter, terminal or nearly terminal on abbreviated vein branches, generally uniseriate or sometimes biseriate, discrete but confluent at maturity in smaller lobes; sporangium with 12(-13-)21-indurated annulus cells; indusium stramineous to ferrugineous, often also dark-centred, persistent, circular, simple or repand, maximum radius 0.36(-0.57-) 0.89 mm; spores dark brown, perispore smooth or forming low, reticulate ridges, sparsely echinulate, variously perforated, exospore 22(-45.58-)62 × 22(-30.82-)40 µm. Chromosome number unknown. — Figs. 1 , 3 A-C.

MATERIAL EXAMINED. — MADAGASCAR: Rakolomalala s.n., région de Sambirano ( P). — MAURITIUS: Ayres s.n., without precise locality ( L); Bewsher s.n., without precise locality ( B, SAM); Boivin s.n., without precise locality ( P); Bory de Saint-Vincent s.n., without precise locality ( L); Bouton s.n., without precise locality ( B); Commerson s.n., without precise locality ( L, P); Düring 1825, without precise locality ( B); Düring s.n., without precise locality ( B 96919); D’Urville 152, without precise locality ( B); Guého 11453, Mt. Corps de Garde, ( P); Lorence 346, Le Pouce Mt., E windward flank, 650 m ( MO); Lorence 390, Mt. Lagrave, S flank, c. 650 m ( MO); Sieber s.n., Fl. Maur. n. 48 ( B); Sieber s.n., Syn. fil. n. 34, without precise locality ( B, K, L, MO, P, S); Sieber s.n., without precise locality ( L); Vesco s.n., without precise locality ( P); sine coll., without precise locality ( B 96913); sine coll., without precise locality ( B 96928); sine coll. s.n., without precise locality ( S); sine coll., without precise locality ( B 96914); sine coll., without precise locality ( B 97038); sine coll. s.n., without precise locality ( BR). — LA RÉUNION: Badré 854, Îlet à Guillaume ( P); Badré 978, route de la montagne St. Denis, à La Possession ( P); Badré 1053bis, Cirque de Salazie, sentier vers La Nouvelle, 1300-1400 m ( P); Badré 1118, Pas de Bellecombe ( P); Bathe s.n., without precise locality ( P); Bernier 1, Cilaos ( P); Bernier 93, without precise locality ( P); Bernier s.n., without precise locality ( P); Berter s.n., without precise locality ( B); Billiet & Jadin 422, route vers le Piton Maïdo, 1600 m ( BR); Billiet & Jadin 511, environs du gîte de la Caverne Dufour, entre Cilaos et Piton des Neiges, 2400 m ( BR); Billiet & Jadin 581, plaine d’Affouches, 1200 m ( BR); Billiet & Jadin 618, forêt de Bébour, 1400 m ( BR); Billiet & Jadin 807, Dos d’Âne, rempart de la rivière Sainte-Suzanne, 1200 m ( BR); Billiet & Jadin 820, plaine des Chicots, environs du gîte de la Roche Écrite, 1800 m ( BR); Billiet & Jadin 887, Bébour, rivière des Marsouins ( BR); Billiet & Jadin 895, Piton Maïdo, 2200 m ( BR); Boivin 891, without precise locality ( B, P); Boivin 892, without precise locality ( B, L); Bosser 11453, sentier du volcan, c. 2000 m ( P); Bosser 11474, sentier du Bras Cabot, plaine des Palmistes, 1400-1500 m ( P); Bosser 11710, La Roche Écrite, 2200-2300 m ( P); Bosser 20437, montée de la plaine des Affouches, 1000-1100 m ( P); Bosser 21205, haut de Brass-Panon, 600 m ( P); Cadet 43, Grande Montée, 1500 m ( P); Cadet 1553, massif de la Fournaise, 2200 m ( P); Cadet 1664, Grand Coin, Dos d’Âne, 800 m ( P); Cadet 1942, pentes du Cirque de Cilaos ( P); Decken s.n., prope Caverne de Musard ( B); Delavary s.n., plaine du Piton des Neiges ( P); De l’Isle 371, ravine du Bras Piton, plaine des Palmistes ( K); De Lessert s.n., without precise locality ( B); De Sloover P 2, au pied du Piton de la Grande Montée, 1600 m ( BR); De Sloover P 38, Piton de Maïdo, 2150 m ( BR); Gaudichaud s.n., without precise locality ( P); Gimalac 70 R, sentier du Piton des Neiges, 3000 m ( BR); Hombron s.n., without precise locality ( P); Houdllet s.n., without precise locality ( B); Keller s.n., Brûlé de St. Denis ( B); Kersten 100, without precise locality ( B); Kersten 101, zweihohen Cap Augéas à Caverne de Musard ( B); Kersten 102, Hellbourg ( B); Olivier s.n., without precise locality ( BR); Onraedt 155, Réserve Forestière de Bébour, ± 1600 m ( MO); Onraedt 69 R 36, plaine des Cafres, au Piton des Forges ( BR); Onraedt 69 R 80, plaine des Cafres, aux sources Reilhac, 1550 m ( BR); Onraedt 69 R 82, plaine des Palmistes, au Piton Desforges, 1550 m ( BR); Onraedt 69 R 107, route forestière de Tévelare, 1300 m ( BR); Onraedt 69 R 122, plaine des Cafres, au Piton Desforges, 1550 m ( BR); Onraedt 69 R 155, Réserve Forestière de Bebour, 1600 m ( BR); Onraedt 70 R, plaine des Osmondes, au Trou Caron, c. 1000 m ( BR); Lépervanche-Mézière s.n., without precise locality ( P); Lotzy T 11, Salazie, 1000 m ( M); Rauh 10235, Petite plaine ( BM); Richard 94, without precise locality ( B); Richard 321, without precise locality ( P); Williams 3449, walk down to cascade de Bras Rouge, Cilaos ( NBG); Vieillard s.n., without precise locality ( B 97037); Vieillard & Deplanche s.n., without precise locality ( L, P); sine coll. 43, without precise locality ( BR); sine coll. 321, without precise locality ( B); sine coll. 361, without precise locality ( P); sine coll. sn., without precise locality ( B); sine coll. s.n., without precise locality ( BR); sine coll. s.n., without precise locality ( L).

WITHOUT INDICATION OF ISLAND. — Sine coll., s.loc. ( B 96927); sine coll., s.loc. ( P [ A only]); sine coll., s.loc. ( B 96929 [ A only]); sine coll. 692, s.loc. ( B); sine coll. 82, s.loc. ( P); Bory de Saint-Vincent s.n., s.loc. ( P [3 sheets]); sine coll. s.n., s.loc. ( P); Splitgerber s.n., Pr. b. sp. ( L); Sieber flora mixta n. 286, s.loc. ( L).

POIRET (1804) first described the species as Polypodium ammifolium , based on a COMMERSON collection made during his stay on Mauritius during the 1770’s. Two sheets of this plant are currently housed in the Lamarck Herbarium in Paris. The sheet numbered 626, named “polyp. ammifolium ”, is here selected as the lectotype. Later authors evidently overlooked this name resulting in the species being described or listed under different names by KAULFUSS (1827), BORY DE SAINT- VINCENT (1833), SIEBER (exsicc.) and FÉE (1857). CHRISTENSEN (1905) initially considered the species to be a form of P. aculeatum (L.) Roth, but in 1932 recognized it as a distinct species.

K AULFUSS (1827) described Aspidium stramineum , giving the origin as C.B.S. (Caput Bonae Spei). The collector of the material was not indicated, but currently it is accepted that the material upon which KAULFUSS based the species originated from Mauritius (B OJER 1837; HOOKER 1862; KUHN 1868). The current location of KAULFUSS’ s pteridophyte collection, that was acquired by RÖMER ( STAFLEU & COWAN 1979) is not known and therefore the collector of the material cannot be determined. Two sheets inscribed by W.J. HOOKER as “ Aspid. stramineum Kaulf. n. sp. ” are currently housed in the Kew Herbarium. These specimens originated from Mauritius and are duplicates of SIEBER’ s Synopsis filicum exsiccatae (number 34). Although HOOKER (1862) stated that SIEBER Synopsis filicum number 34 is Aspidium stramineum Kaulf. there is no proof that KAULFUSS based the species on a SIEBER collection and thus authentic material of Aspidium stramineum remains unlocated.

BORY DE SAINT- VINCENT also obtained material from Mauritius and in 1833 described the plant as Hypopeltis mauritiana . Neither the type, nor any other material that can be considered original, of this species has yet been located. There is no doubt, however, that the plants are of the same species because B ORY DE S AINT- V INCENT described the stipe and rachis as “squamoso-tomentosis” and the pinnules as “argutè crenatis, supernè mucronatis”. The only other Polystichum species occurring on Mauritius, P. crinulosum , does not conform to this description.

Frans W. S IEBER spent eleven weeks on Mauritius during late 1822 and early 1823 ( GUNN & CODD 1981). In the exsiccatae of his Flora Mauritiana he listed the plant as Aspidium vestitum . Since the epithet had already been used by SWARTZ (1801), PRESL renamed the plant P. sieberianum citing SIEBER’ S Flora Mauritiana, ed. 1, suppl. n. 48 exsiccata. SIEBER, however, did not provide diagnoses for his plants but merely lists them in his exsiccatae. Since PRESL did not provide a diagnosis either, both names are invalid under Art. 32.1 ( GREUTER et al. 2000).

FÉE (1857) based his description of P. schizolobium on a collection made by DE MONTBRISON on La Réunion. The type of this collection appears to be missing as a search in BASSA, BORD, FI, L, NTM, P, PC and STR proved fruitless .

DIAGNOSTIC FEATURES AND RELATIONSHIPS. — Polystichum ammifolium is characterized by the closely and minutely fimbriated margins of the larger stipe and rachis paleae. Perhaps more diagnostic, however, are the paleae that occur adaxially and abaxially on the lamina which bear long, mainly basally directed, marginal outgrowths. Similarly structured paleae have been observed in P. vestitum (G. Forst.) C. Presl from New Zealand and may suggest an affinity. Polystichum ammifolium belongs to section Lasiopolystichum Daigobo.

VARIATION. — Two forms can be distinguished within Polystichum ammifolium . The Mauritian form is characterized by shorter and broader fronds and is generally less dissected than the La Réunion form. The pinnules of the Mauritian form are generally ovate to broadly ovate in outline and shallowly and obtusely lobed. The most diagnostic feature of this form is the stipe which is densely covered by large chartaceous and stramineous, ovate to broadly ovate paleae. The La Réunion form has much longer and narrower and generally more deeply dissected pinnules of which the margins are sharply dentate to aristate. The paleae on the stipe are conspicuously dimorphic with the larger paleae more widely spaced, membranous and stramineous or centrally dark brown, nitid and crustaceous. In spite of these variations the paleae do not differ micromorphologically. Also, the paleae occurring on the lamina surfaces do not differ. It is therefore suggested that the forms be retained as a single species. CORDEMOY (1895) recognised two morphological forms on La Réunion, but confered no formal taxonomic status to them.

DISTRIBUTION AND ECOLOGY. — Polystichum ammifolium is confined to Madagascar, Mauritius and La Réunion. On Mauritius the species occurs at elevations between 500-650 m in dry evergreen thickets and in lower montane wet forests ( LORENCE 1978). Dry evergreen thickets that are now confined to the western mountain slopes and flanks fall within the rain shadow area and receive an annual precipitation of 1000-1600 mm. The lower montane wet forests are largely confined to the central plateau of the island and are charcterized by a much richer flora. Annual precipitation in these forests range between 1800 and 4200 mm.

On La Réunion the species occurs at elevations ranging from 600-2200 m and grows in a number of plant communities. The principal zones, as defined by BADRÉ & CADET (1978), in which the species occurs are megathermic dry sector vegetation, lowland forests, high altitude hygrophylic formations and high altitude ericoid vegetation. Although the species largely occurs on moist forest floors it is also found in rock crevices, especially of lava fields at higher elevations.

In Madagascar the distribution of the species appear to be restricted, having been recorded only from the northern Sambirano region.

Figures

Fig. 1. — Polystichum ammifolium: A, middle pinnae of lamina; B, abaxial surface of a basal acroscopic pinnule; C, rhizome. A-B, Cadet 1164 (P); C, Guého 11453 (P).

Fig. 3. — Stipe and lamina paleae in Polystichum species. — Polystichum ammifolium: A, stipe palea, Boivin 822 (B); B, lamina palea (adaxial surface), Rakolomalala s.n. (P); C, basal part of B showing the cellular structure. — Polystichum crinulosum: D, stipe palea, s.coll. s.n. (P); E, apex of D showing the cellular structure; F, rachis palea, s.coll. s.n. (P); G, apex of F showing the cellular structure. — Polystichum kalambatitrense: H, stipe palea. Humbert 12158 (P); I, lamina palea (abaxial surface), Humbert 11914 (P). — Polystichum luctuosum: J, stipe palea. Roux 2268 (NBG); K, lamina palea (abaxial surface), McDonell 34 (BM).