Dryopteris comorensis (Tardieu) Fraser-Jenk.

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 : 34-38

4. Dryopteris comorensis (Tardieu) Fraser-Jenk.

( Figs 14 ; 15 )

Thaiszia 4 (1): 34 (1994). — Dryopteris inaequalis (Schltdl.) Kuntze var. comorensis Tardieu, Notulae Systematicae (Paris) 15 (2): 162 (Apr. 1956).

— Type: Comores, environs de Nioubadjou , Humblot 254 (holo-, BM000801045 !; iso-, K!, P00220415 !) .

OTHER MATERIAL EXAMINED. — Comoro Islands. Grande Comore, à 5 km au Sud-est de Nioumbadjou, 600 à 700 m d’alt., 23.XI.1975, Coulon 277 ( MO 4374549). — Village de Kourani, 770 m, 11°51’S, 43°25’E, 15.II.1975, Floret 950 ( MO 4374543, P 00220424). — Centre-Sud, entre Kourani et Dombéni vers 500 m d’alt., 15.II.1975, Floret 957 ( P 00220421). — Environs de Nioumbadjou , 400-500 m, IV.1911, Humblot s.n. ( P 00220417). — Comore Islands , 1884, Humblot 254 ( BM 000801045, K, P). — Massif du Kartala, versant ouest, 11°45’S, 43°19’E, 1900 m, forêt dense humide de montagne, Rakotondrainibe 6815 ( P 00312090, P 00312091, P 00312092).

Madagascar. Antsiranana, Parc national de la Montagne d’Ambre, environs du Lac Texier, rive NO. 1070 m, 27.VI.1992, Rakotondrainibe 1739 ( P 00100256) . — Antsiranana, Parc national de la Montagne d’Ambre, environs du lac Texier, rive NO, forêt primaire, cirque volcanique, 27.VI.1992, Rakotondrainibe 1740 ( P 00100257, P 00100258, P 00100259).

DESCRIPTION

Plants terrestrial. Rhizome decumbent. Fronds crowded, suberect to arching, up to 1.9 m long; stipe proximally castaneous, stramineous higher up, sulcate adaxially, up to 830 mm long and 15 mm in diameter at the base, proximally densely scaled, moderately to sparsely scaled higher up, the scales ferrugineous, chartaceous, rugose, linearacuminate, up to 30 × 5 mm, adnate, the margins regularly set with capitate glands and twisted pluricellular, mostly pluriseriate outgrowths, the apex filiform, twisted, terminating in an oblong cell; lamina anadromous, catadromous towards the apex, broadly ovate to deltoid, up to 1.1 × 0.78 m, to 3-pinnate, with up to 15 petiolated pinna pairs, pinnae near the apex become sessile and increasingly basiscopically decurrent; rachis stramineous, adaxially sulcate, initially moderately scaled, sparsely scaled later, the scales similar to, but smaller than those on the stipe, up to 12 × 3 mm; pinnae petiolate, the petiole up to 45 mm long, spaced or overlapping, near opposite to alternate, basal pinna pair longest, to 2-pinnate, basiscopically developed, inaequilaterally lanceolate, up to 440 × 225 mm, pinnae towards the apex oblong-acuminate, with up to 10 petiolated pinnule pairs; pinna-rachis stramineous, adaxially sulcate, narrowly winged towards the apex, sparsely to moderately scaled, the scales stramineous, thinly chartaceous, sessile or short-stalked, lanceolate-caudate to narrowly lanceolate-caudate, up to 13 × 2.3 mm, narrowly to broadly cuneate, irregularly set with glands along the margins and laminae, the margins also with long and twisted pluricellular outgrowths, the apex terminates in a series of oblong cells; pinnules petiolate, the petiole up to 2 mm long, proximally widely spaced or overlapping, proximal basiscopic pinnule longest or not, acroscopic pinnule on basal pinnae oblong-acuminate, up to 87 × 27 mm, 1-pinnate, basiscopic pinnule on basal pinnae oblong-acuminate, up to 135 × 45 mm, to 1-pinnate, with up to 6 petiolated segment pairs; pinnule-rachis stramineous, adaxially sulcate, pronounced abaxially, sparsely haired adaxially, sparsely to moderately scaled abaxially, the scales similar to those on the pinna-rachis, up to 5 × 1.4 mm; segments herbaceous, petiolate, the petiole up to 0.5 mm long, sessile and increasingly basiscopically decurrent along the costa towards the apex, narrowly lanceolate to oblong-acuminate, up to 27 × 10 mm, lobed, the lobes oblong-obtuse, up to 5 × 4 mm, shallowly denticulate, adaxially with a few hairs along the costule, abaxially sparsely to moderately set with hairs and scales along the costule and veins, the hairs isocytic, up to 2.5 mm long, the scales stramineous to ferrugineous, thinly chartaceous, stalked, subulate-caudate, up to 2.5 × 0.6 mm, the apex terminates in a series of oblong cells. Venation evident, lateral veins in segment lobes pinnately branched, vein branches end in the teeth near the margin. Stomata mostly of the polocytic type, (34-)40(-46) µm long. Sori essentially 2-seriate on segments, discrete or touching at maturity, medial on predominantly anadromous vein branches, up to 1 mm in diameter at maturity; indusium ferrugineous, firmly herbaceous, reniform, entire or shallowly repand, strongly recurved. Sporangium stalk simple, glandular, or haired, capsule with (13-)15(-18) indurated annulus cells, epistomium (3-)4(-6)-celled, hypostomium 4(-6)-celled. Spores brown, 64 per sporangium, exospore (34-)37(- 44) × (20-)23(-26) µm.

DIAGNOSTIC FEATURES AND RELATIONSHIPS

Dryopteris comorensis is separated from other species in the Mascarene region by the rugose scales, which form a dense covering on the lower half of the stipe. These scales bear capitate glands and numerous long and twisted outgrowths along the margins. Although similar marginal outgrowths may occur in D. pentheri , that species does not occur on Grande Comore, neither does it bear unicellular oblong glands or 2-celled hairs along the lamina axes and veins. Scales along the pinnarachis are often somewhat bullate. The stoma size is also smaller, (34-)40(-46) µm, which suggests it being diploid, rather than (34-)53(-72) µm as in D. pentheri , which is tetraploid.

Fraser-Jenkins (1986) failed to include the taxon in his classification. I see no evidence of this species being related to Dryopteris inaequalis (Schltdl.) Kuntze , as suggested by viewing it as a variety of this species (Tardieu-Blot 1956a: 162). I support Fraser-Jenkins (1994) in recognizing it as a distinct species.

DISTRIBUTION AND HABITAT

Dryopteris comorensis occurs on Grande Comore, also known as Ngazidja (11°45’S, 43°19’E), and on Montagne d’Ambre (c. 12°32’S, 49°10’E), in northern Madagascar ( Fig. 16 ). The species is restricted to the evergreen rain forests and occurs at altitudes ranging between 400 to 1900 m on Mount Kartala. Both Mount Kartala and Montagne d’Ambre are of volcanic origin.

Figures

FIG. 14. — Specimen of Dryopteris comorensis (Tardieu) Fraser-Jenk., Rakotondrainibe 1739 (P00100256). Photo: MNHN, Paris Herbarium, 2009.

FIG. 15.— Indumentum and indusium of Dryopteris comorensis (Tardieu) Fraser-Jenk.:A, stipe scale; B, rachis scale; C, pinna-rachis scale; D, costa scale; E, indusium, F, G, hairs from abaxial lamina surface. Floret 957 (P00220421). Scale bars: A-E, 1 mm; F, G, 0.1 mm.

FIG. 16. — Distribution of Dryopteris comorensis (Tardieu) Fraser- Jenk.(z) and D.manniana (Hook.) C.Chr.(Δ) in Madagascar and neighbouring Indian Ocean islands.