Polystichum crinulosum (Desv.) J.P. Roux

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 : 271-272

2. Polystichum crinulosum (Desv.) J.P. Roux

Novon 6: 202 (1996). — Aspidium crinulosum Desv., Mém. Soc. Linn. Paris 6: 249 (1827). — Lectotype (designated by ROUX 1996): Sine coll. s.n., habitat in insula Mauritii ( Mauritius), ( P!; iso-, B 96929!); only known material.

Plants terrestrial. Rhizome unknown but probably short and erect to suberect. Stipe castaneous, adaxially sulcate, to 3 mm in diameter at the lamina base, densely paleated, the paleae appear heteromorphous, the larger paleae bicolorous, centrally ebeneous, nitid and crustaceous with a narrow ferrugineous to stramineous, membranous margin, sessile, ovate to narrowly ovate, cordate, the margins moderately beset with short, straight, simple or branched, emarginate or forked outgrowths which reduce in size and number towards the apex, the apex terminates in a short acicular cell or a small elliptic thin-walled cell, to 8 × 4 mm, the smaller paleae ferrugineous to stramineous, chartaceous, sessile, narrowly ovate to narrowly triangular-hastate, cordate, the margin proximally with a few short, straight, simple or curved, emarginate or forked outgrowths which reduce in size and number towards the apex, the apex terminates in a short acicular cell or a small thin-walled cell; lamina 2-pinnate, with up to 24 pairs of stalked pinnae, narrowly ovate, to 440 mm long, the pinnae opposite to alternate, closely spaced, proximally somewhat more widely spaced, the proximal pinnae reduced; rachis with proliferous buds near the apex, castaneous to stramineous, adaxially sulcate, densely paleated, the paleae ferrugineous to castaneous, chartaceous, or proximally often centrally ebeneous, nitid, crustaceous, with a narrow ferrugineous, membranous margin, sessile, narrowly ovate to subulate-hastate, cordate to cordate-imbricate, the margins proximally moderately beset with short straight or curved, often emarginate marginal outgrowths which reduce in size and number towards the apex, the apex is often multiseriate and eglandular or it terminates in a short acicular cell, or a small thin-walled cell, to 3.5 × 1 mm; pinnae 1-pinnate, with up to 16 pairs of stalked pinnules, oblong-attenuate, slightly auriculate acroscopically, the middle pinnae to 125 mm long, to 25 mm wide; pinnarachis stramineous, adaxially sulcate, densely paleated, the paleae ferrugineous, chartaceous, sessile, narrowly ovate to subulate-hastate, cordate, the margins proximally with short straight or curved, simple or branched outgrowths which rapidly reduce in size and number towards the apex, the apex terminates in a short acicular cell or a small thin-walled cell, to 3 × 0.8 mm; pinnules opposite to alternate, closely spaced but not overlapping, short-stalked proximally, sessile towards the apex, firmly herbaceous, dark green adaxially, slightly paler abaxially, inaequilateral, ovate to rhombic, basiscopically cuneate, acroscopically cuneate to truncate and auriculate, shallowly obtusely lobed to serrate, the proximal acroscopic pinnules deeply incised acroscopically to form a nearly free broadly obovate lobe, to 14 × 7 mm, adaxially glabrous, evidently glabrous abaxially. Venation obscure adaxially, evident abaxially. Sori circular, to 1.5 mm in diameter, medial or supramedial on modified vein branches, essentially uniseriate, discrete at maturity; sporangium with 12(-14-)16- indurated annulus cells, stalk glandular; indusium stramineous, black centred, persistent, circular, shallowly repand, maximum radius 0.87(-0.97-) 1.07 mm. Spores dark brown, perispore folded to form a close reticulum of inflated and compressed ridges, the ridges echinulate, the ridges and areas between perforated, the exospore 30(-35.32-)42 × 24(-27.8-)34 µm. Chromosome number unknown. — Figs. 2 , 3 D-G.

DESVAUX described the species in 1827, giving the locality as “Habitat in montosis. C. Bonae spei” (Caput Bonae Spei). The sheet selected as lectotype of the species ( ROUX 1996 ), however, gives the locality as “Habitat in insula Mauritii”. The latter locality is taken as correct as the species does not conform to any of the known African taxa .

KUHN (1868) considered the name to be synonymous with Polystichum ammifolium (Poir.) C. Chr. , whilst CHRISTENSEN (1905) believed it to be a form of P. aculeatum (L.) Roth. It is, however, distinct from any of the known taxa from the region.

DIAGNOSTIC FEATURES AND RELATIONSHIPS. — Polystichum crinulosum is characterized by the presence of proliferous buds on the rachis near the frond apex, the presence of glandular cells along the sporangium stalk and the palea morphology. The paleae apices are generally short and blunt and often multiseriate and eglandular, terminating in a short acicular cell or a small thin-walled cell. The palea morphology suggests that it should be included in section Metapolystichum Tagawa.

DISTRIBUTION AND ECOLOGY. — Polystichum crinulosum is known only from Mauritius, and nothing is known about its ecology. DESVAUX merely states “Habitat in montosis”. The species is known only from the type collection. Because of the large-scale destruction of the natural vegetation of the island, the species may well now be extinct .

Figures

Fig. 2. — Polystichum crinulosum: A, distal pinnae showing proliferous buds; B, basal part of lamina; C, abaxial surface of a fertile pinnule. All drawn from s.coll. s.n. (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).