Dryopteris pentheri (Krasser) C.Chr.

Roux, Jacobus P., 2011, The fern genera Dryopteris and Nothoperanema (Dryopteridaceae) in Madagascar and neighbouring Indian Ocean islands, including Saint Paul, Adansonia (3) 33 (1), pp. 7-67 : 42-46

6. Dryopteris pentheri (Krasser) C.Chr.

( Figs 19 ; 20 )

Index filicum: 284 (18 Nov. 1905). — Nephrodium pentheri Krasser, Annales des Kaiserlich-Königlichen Naturhistorischen Hofmuseums , Wien 15: 5, 6 (1900).

— Type: South Africa, Van Reenens Pass, 4.III.1895, F. Krook s.n., sub Penther Plantae Austro-Africanae 36 (lecto-, W 8042 ! designated by Pichi Sermolli [1984: 329]; isolecto-, BM!),.

Dryopteris inaequalis sensu Tardieu, Flore de Madagascar et des Comores (Plantes Vasculaires), 5e Famille. Polypodiacées (sensu lato) 5 (1) Dennstaedtiacées. (10) Aspidiacées ): 315 (May 1958), pro parte, non (Schltdl.) Kuntze (1891: 813).

MATERIAL EXAMINED. — Madagascar. Route d’Anjozorobe, prés d’Analabe, XII.1958, Bosser 12329 ( MO 4405417). — Route d’Arivonimamo, 1958, Bosser 12344 ( MO 4405414). — Andramasina, XII.1958, Bosser 12446 ( MO 4405413). — Route de Manankaraly, III.1957, Bosser 12871 ( MO 4405415). — Ankaratra, V.1962, Bosser 16183 ( MO 4405425). — P.K. 39 route du sud, ravin humide, III.1953, Bosser 6203 ( MO 4405416). — Imarina, 1881, Cowan s.n. ( BM 000800959, BM 000800960, BM 000800981, BM 000800985, BM 000800998, BM 000801020, BM 000801031, BM 000801044). — Fianarantsoa, 1879, Cowan s.n. ( BM 000801030). — Prov. Tananarive, vicinity of Station forestière Antsampandrano, disturbed prairie, 1750 m, 23.I.1975, Croat 29124 ( MO 3295933). — Prov. Fianarantoa, forest and forest edge along Route 7, 113-116 km N of Fianarantsoa, 1580-1590 m, 28.I.1975, Croat 29928 ( MO 3295935). — Massif de l’Anakaratra, flanc oriental duTsiafajavona, reste de forêt, 1700-2000 m, 15.VII.1928, Decary, Humbert & Swingle 4568 ( BM 000801032). — Interior, near waterfall Ramainandro, Elliot 1965 ( K). — Ambohimitombo forest, 19.I.1895, Forsyth Major 180 ( BM 000800986, K). — Prov. Imerina, IV.1884, Hildebrandt 3529 ( K, M, US 815398). — Madagascar, V.1880, Kitching s.n. ( K, A only). — Ilafy, Tananarive, 6.I.1970, Onreadt 70M66 ( US 3005426). — Moramanga, c. 900 m, Regenwald, Schlieben 8109 ( M). — La Mandraka, c. 1000 m, Regenwald, 7.XII.1959, Schlieben 8137 ( BM, K, M, 2 sheets, PRE, US 3001350). — Bord de l’eau à l’ombre Tsimbazaza, 14.VII.1885, sine coll. s.n. ( P 00349496). — Madagascar, sine coll. 68 ( NY, US 719837). — Madagascar, sine coll. 87 ( NY, US 719841). — Province du Vakinankaratra, Distr. d’Antsirabe, fentes des rochers sur la pente interne du cratère du Tritriva vers 1800 m d’alt., 16.XI.1972, Viguier & Humbert 1294 ( P 00349498).

Réunion. Fissures aux environs du Piton Maido, Grand Bénard, 2200 m, 22.XI.1968, Cadet 1751 ( P 00349598). — Sous-bois de la forêt hygrophile, forêt de la Mare à Joseph Cilaos, 1400 m, 7.II.1969, Cadet 1904 ( P 00349599, P 00349600). — Clairière dans la forêt du Grand Matarum Cilaos, 1600 m, 23.III.1974, Cadet 4582 ( P 00349596, P 00349597). — Cilaos Distr., footpath from Cilaos thermal baths to Bras Rouge cataract, on earth bank with Polystichum ammifolium , 1100 m, 4.X.1984, Jacobsen 5608 ( FR).

DESCRIPTION

Plants terrestrial or epilithic. Rhizome short-decumbent, sparsely branched, up to 20 mm in diameter, set with roots, closely spaced stipe bases, and scales, the scales stramineous to ferrugineous, chartaceous, broadly attached, linear, oblong or narrowly ovate, up to 37 × 6 mm, truncate, the margins irregularly set with long, twisted, pluricellular filiform outgrowths, the apex filiform, twisted. Fronds caespitose, erect to arching, up to 1.8 m long; stipe proximally castaneous, brown to stramineous higher up, proximally adaxially flattened, shallowly sulcate higher up, up to 485 mm long and 10 mm in diameter, proximally densely scaled, the scales higher up fugaceous, stramineous to ferrugineous, chartaceous, the larger scales up to 40 × 7 mm, broadly attached, the smaller scales sessile or short-stalked, narrowly lanceolate to filiform, cordate to cuneate, the margins irregularly set with long, twisted, pluricellular filiform outgrowths and often also with scattered glands, the apex filiform; lamina herbaceous to firmly herbaceous, ovate to ovate-triangular, up to 780 mm long, 2-pinnate to 3-pinnate, anadromous, catadromous towards the apex, with up to 16 petiolated pinna pairs; rachis stramineous, adaxially shallowly sulcate, becoming narrowly winged towards the apex, initially moderately scaled, the scales fugaceous, broadly attached or short-stalked, narrowly lanceolate to linear, up to 7 × 2 mm, cuneate, the margins irregularly set with long filiform outgrowths, often also with scattered glands, the apex filiform, twisted; pinnae petiolate, the petiole up to 18 mm (rarely to 38 mm) long, the basal pinna pair inaequilaterally ovate to narrowly ovate, narrowly lanceolate to oblong-acuminate towards the lamina apex, to 2-pinnate, basal pair the longest, mostly basiscopically developed, up to 315 × 185 mm, opposite to alternate, basally widely spaced, often somewhat imbricate higher up, with up to 9 petiolated pinnule pairs; pinna-rachis adaxially shallowly sulcate, the sulcus confluent with that of the rachis, pronounced abaxially, narrowly winged distally, abaxially moderately to sparsely set with scales and hairs, the scales and hairs stramineous to ferrugineous, the scales chartaceous to membranous, broadly attached or short-stalked, narrowly to broadly cuneate, up to 5 × 1.6 mm, the margins irregularly set with long pluricellular, filiform outgrowths, the apex filiform, twisted, up to 5 × 1.6 mm, the hairs are of three types: 1) unicellular oblong glands, 2) bicellular hairs with straight or oblique transverse walls, and 3) pluricellular simple or branched, mostly isocytic hairs often bearing a single glandular cell near the base; pinnules petiolate, petiole up to 3 mm long, aequilaterally to inaequilaterally lanceolate to oblongacuminate, basiscopically decurrent, 1-pinnate to lobed, acroscopic pinnule on the basal pinnae up to 90 × 35 mm, basiscopic pinnule on the basal pinnae up to 112 × 42 mm, widely spaced or imbricate; pinnule-rachis adaxially shallowly sulcate, pronounced abaxially, narrowly winged, the wing continuous with that of the pinna-rachis, variously set with scales, isocytic- and 2-celled hairs; segments widely spaced to imbricate, ovate to oblong-obtuse, up to 22 × 9 mm, basiscopically decurrent, lobed, the lobes serrate, adaxially glabrous, with oblong glands along and between the veins, or with a few pluricellular mostly isocytic hairs along the costule, abaxially sparsely set with unicellular oblong glands (60-)137(-260) mm long, 2-celled hairs, and isocytic and/or moniliform hairs, those near the segment base often with a glandular cell near the base, and filiform scales, the scales short-stalked, the stalk often with one or more glandular cells, hairs and scales mostly occur along the costule and veins. Venation anadromous, becoming catadromous towards the lamina and pinna apex, pinnately branched in the segments, vein branches pinnately branched, forked or simple near the apex, evident, ending in the teeth near the margin, endings slightly enlarged and often conspicuous adaxially. Stomata of the anomo- and polocytic types, (34-)53(-72) mm long. Sori circular, medial on predominantly anadromous vein branches, discrete, up to 1.8 mm in diameter at maturity, essentially uniseriate; sporangium stalk simple, or with one or more glandular cells, but mostly with a long multicellular, uniseriate hair, capsule with (11-)13(-20) indurated annulus cells, epistomium (3-)6(-8)-celled, hypostomium (3-)6(-8)-celled; indusium persistent, pale brown, firmly herbaceous, reniform, entire, repand, or erose, (rarely glandular along margin), often strongly revolute, to 1.8 mm in diameter. Spores ellipsoidal, monolete, perispore folded into tubercules or reticulate ridges, finely rugose to ruminate, (38-)45(-60) × (27-)31(-40) mm (Tryon & Lugardon 1990: 426, fig. 159.21). Chromosome number: 2n = c. 164 (Vida in Widén et al. 1973: 2129).

REMARKS

The spores of Viguier & Humbert 1731 (P00349497) are highly abnormal and may be indicative of it being a hybrid. Other features of the specimen – stoma size and the presence of 2-celled hairs – are typical of D. pentheri .

DIAGNOSTIC FEATURES AND RELATIONSHIPS

Dryopteris pentheri is an exteremely variable species difficult to separate from other species using macromorphological features. Micromorphological features separating it from other Dryopteris species in the region are the oblong glands ( Fig. 19E ) and 2-celled hairs ( Fig. 19D ), occurring along the frond axes and veins, and the larger stomata ( Table 1 ).

VARIATION

Dryopteris pentheri is extremely variable in gross morphology and attempts by several authors to separate this species based on macromorphological characters have failed. Micromorphological characters and cytological observations are more reliable in separating D. pentheri from other taxa. Micromorphological features of significance are the presence of bicellular hairs, unicellular gland length, as well as stoma and spore size. These features, however, all show some variation. Bicellular hairs occurring abaxially on the lamina were observed on the costa, costules or veins in 64.5% of the collections studied. These hairs mostly occur centrally on an epidermal cell, but rarely also near the distal end of a cell. The periclinal wall of the epidermal cells bearing the hairs is flat or the hairs are positioned on a low but prominent bulge. The transverse wall between the two hair cells may be straight or oblique. Unicellular glandular hairs were observed in 96.8% of the collections studied. These oblong hairs, 60-260 mm long, are positioned on the epidermal cells in a similar fashion as bicellular hairs. Pluricellular hairs 6 to 21 cells long occur adaxially and abaxially on or near the costae, costules and veins. They are of the isocytic or moniliform type and are positioned centrally on or near the distal margin of an epidermal cell. They often bear a single (rarely 2) glandular cell near the base. The indusium also shows significant variation in size and margin sculpture. In a few cases, glands have been observed along the indusium margin.

DISTRIBUTION AND HABITAT

Dryopteris pentheri is widespread in the eastern and western mountainous regions of sub-Sahara Africa, Madagascar and Réunion ( Fig. 20 ). Although predominantly confined to moist forests, the species occurs in open habitats at higher elevations. In these habitats, the plants are mostly confined to boulder bases and rock crevices on ridges and montane streams. In grassland habitats, the species is exposed to regular burning, but this appears to have little effect on the subterranean rhizome. In Madagascar, it is confined to the central mountainous regions, at elevations ranging between 1580 and 2000 m, but on Réunion, it occurs in moist montane forests and in seasonally wet forests from 1100 to 2200 m, where the plants often become seasonally dormant.

Figures

FIG. 19. — Specimen of Dryopteris pentheri (Krasser) C.Chr., Croat 29928 (MO3295935).

FIG. 20. — Indumentum and indusium of Dryopteris pentheri (Krasser) C.Chr.: A, stipe scale; B, rachis scale; C, isocytic hair from abaxial lamin surface; D, 2-celled hair; E, unicellular oblong hair; F, indusium. Schelpe 6018 (BOL). Scale bars: A, B, F, 0.5 mm; C-E, 0.1 mm.