Cyathea borbonica Desv. var. sevathiana Th.Janssen & Rakotondr., 2006

Janssen, Thomas & Rakotondrainibe, France, 2006, A revision of the fern family Cyatheaceae in the Mascarene Islands, Adansonia (3) 28 (2), pp. 213-241 : 218-226

1. Cyathea borbonica Desv. var. borbonica ( Figs 1 ; 7C ; 8A )

Der Gesellschaft naturforschender Freunde zu Berlin Magazin für die neuesten Entdeckungen in der gesammten Naturkunde 5: 328 (1811); Christensen, Dansk botanisk arkiv 7: 21 (1932), excl. specim. madag.; Tardieu in Humbert, Flore de Madagascar et des Comores, fam. 4: 13, f. 1, 4-5 (1951), excl. specim. madag.; Tardieu, Notulae Systematicae (Paris) 16: 156 (1960). — Cyathea mascarena “Sw. ” Desv., Prodrome de la famille des fougères: 322 (1827), nom. superfl. — Alsophila borbonica (Desv.) R.M.Tryon, Contributions from the Gray herbarium 200: 30 (1970). — Type: habitat in insula borboniae, Anon. s.n. in hb. Desvaux p.p. (lecto-, sterile fragment, P!, here designated); Grand Étang, sentier menant du parking vers le point de vue, 21°05’44’’S, 55°38’39’’E, 557 m, 30.III.2005, Janssen et al. 2670 (epi-, P!, here designated; isoepi-, P!).

Cyathea borbonica Poir. in Lam., Encyclopédie méthodique (Botanique) suppl. 2: 425 (1812), nom. illeg., non Desv. (1811). — Type: Bourbon, Bory de St-Vincent s.n. in hb. Desfontaines (holo-, FI!).

Cyathea canaliculata auct. non Willd.: Cordem., Flore de l’île de la Réunion 39 (1895).

ADDITIONAL MATERIAL EXAMINED. — Réunion. Bonnet Carré, Cilaos, 15.XI.1973, Badré 915 (P). — Brûlé de Ste-Rose, 21.XI.1973, Badré 986 (P). — Sentier de la

Roche Écrite, 25.XI.1970, Barclay 2053 (MAU). — Barthe 56 (BM). — Bédier s.n. (P). — Brûlé, 1891, Bédier 46 (P). — Bélanger s.n. (P). — Boivin s.n. (B [2], G, P). — Boivin 898 (B, G, P). — Bory de St- Vincent 330 (P). — St-Philippe, V.1957, Bosser 11759 (P). — Bréon s.n. (P [4]). — Tèvelave, 24.I.1962, Cadet 93 (REU). — Plaine des Chicots, 25.XI.1970, Cadet 2899 (REU). — Plaine des Palmistes, 14.VIII.1973, Cadet 4344 (REU). — Commerson s.n. (P-JU, putative isolectotype). — Delavaux s.n. (P). — Delessert s.n. (G). — Garnier 12 (BM). — VII.1837, Gaudichaud s.n. (G, P). — Gaudichaud s.n. (B, P [3]). — Houllet s.n. (P). — Héribaud s.n. (P). — De l’Isle 580 (P). — Grand Étang, sentier menant du parking vers le point de vue, 21°05’44”S, 55°38’39”E, 557 m, 30.III.2005, Janssen et al. 2675 (MO, P); 2676 (MO, P); 2678 (MO, P). — St-Philippe, forêt de Mare Longue, sentier botanique, puis sentier GR R.2, 21°21’18”S, 55°44’22”E, 190-300 m, 31.III.2005, Janssen et al. 2697 (MO, P). — Forêt de Bébour, sentier pédagogique de Bras Cabot, 21°07’27”S, 55°34’25”E, 1345 m, 2.IV.2005, Janssen et al. 2726 (MO, P). — Lépervanche-Mézières 2 (P). — Lépervanche-Mézières 3 (P). — Limminghe s.n. (P). — Petite Plaine, 6.XI.2004, Rakotondrainibe et al. 6919 (P). — Richard s.n. (P). — Richard 32 (P). — Richard 83 (K). — Richard 236 (P). — Vieillard s.n. (B, P). — Vieillard et Deplanche s.n. (W). — Anon. s.n. (P [6]). — Anon. s.n. in hb. Kuhn (B). — Anon. s.n. in hb. Roem (BM).

Without or with doubtful locality. [ Mauritius?], Boivin s.n. (B, P [4]). — [ Mauritius?], Hooker s.n. (P). — Cult. Hort. Parisi, II.1857, Houllet s.n. (P). — McGregor s.n. (BM). — Richard s.n. (P). — Sieber s.n. (P). — Anon. s.n. (BM [3], P [2]).

DESCRIPTION

Trunk: 1-6(-8) m tall, diameter 4-7(-9) cm, rarely branched, its surface smooth to muricate, dark brown, petiole bases persistent in upper 30 cm, but soon caducous and leaf scars exposed.

Leaf scars: (1-)4-5 × 1-2 cm, rounded to elliptical, displaying 3-5 shallow very small to rather large cavities on their lower rim.

Crown: flat, petioles and rachises rather straight and spreading horizontally, sometimes deflexed, young leaves erect, arranged in approximately eight orthostichies forming distinct pseudoverticils.

Trunk apex: hidden by close standing sigmoid petiole bases, some dead rachises persistent and hanging from the apex, their pinnae having fallen off.

Petiole: 2-5(-7) cm long, diameter 1.7-2.5 cm, slightly muricate at its base, green to stramineous, abaxial face brown to castaneous, rarely reddish to atropurpureous on both faces, one to several line(s) of very distant white to light brown small aerophores on either side.

Lamina: bipinnate, narrowly elliptical to oblanceolate, (110-) 150-210 cm long, 50-75 cm wide at its widest point ([60-] 85-100 cm from base of lamina), bearing 35-50 pinna pairs, basal pinnae gradually reduced in size, almost attaining the petiole base, retroflexed and more or less conduplicate, lamina herbaceous to subcoriaceous, pale green on abaxial face, shiny green on adaxial face, rachis coloured like petiole.

Largest pinnae: (20-) 25-36 cm long, spaced by 3.5-4.5 cm, separate to overlapping, costae and costules stramineous, often tinged with red on abaxial face.

Largest pinnules: (1.8-)2-3 × (0.4-) 0.5-0.6 cm, sessile to petiolulate with obtuse to truncate base, in lower 1/3 of pinnae somewhat biauriculate, becoming progressively adnate in upper 1/2 of pinnae and then often proximally decurrent, oblong, slightly falciform, margin subentire, apex obtuse to acute, rarely rounded, with crenulate to serrulate margin, veins once furcate.

Scales and hairs: scales of the petiole base ascending up to 15 cm, caducous, narrowly triangular, 2.5-3 × 0.15-0.2 cm, apex crispate, dull brown with a rather broad light brown (usually eroded) margin, appressed and with a tendency to agglutinate among themselves (their apices usually free), adaxial surface of costae with light brown, tortuous multicellular hairs, otherwise all axes glabrous except for scattered (often acaroid) squamules, adaxial face of rachis without hairs, adaxial face of costulae and veins in the pinnule apices with appressed straight stiff hyaline acicular hairs (often caducous in older leaves).

Sori: subcostular, separate, covering the pinnules from 3/4 to entirely, indusia globular, membranous, dehiscing in 2 or 3 lobes, receptacle capitate to short columnar, with short inconspicuous paraphyses.

Spores: trilete, diameter (dehydrated) 50-60 µm, surface covered by slender rodlets.

DISTRIBUTION

Réunion, endemic.

ECOLOGY

From 200 to 1400 m, i.e. lower to higher elevation evergreen forests, frequently on forest margins and in somewhat open habitats.

REMARKS

The type variety of Cyathea borbonica is endemic to Réunion and can be easily distinguished from the two closely related varieties on Mauritius, var. latifolia and var. sevathiana , by its habit and, in herbarium specimens, with the help of pinnule dimensions and scale morphology. The specimens Bosser 11759 and Boivin 898 are attributed to the type variety despite having small, but fertile leaves with pinnae only 15- 18 cm long and pinnules up to 1.5 cm long.

VERNACULAR NAMES

Fanjan mâle (making reference to the base of the trunk not being broadened by adventitious roots), fanjan.

TYPIFICATION AND SYNONYMY

Desvaux (1811: 328) did not indicate any original collections and provided a rather vague description of the species as bipinnate with sessile, but not adnate pinnules. Fertile structures are not mentioned. A specimen from Desvaux’ herbarium, bearing a label in Desvaux’ writing including the description exactly as published has been traced at P. The place of publication has, probably later, been added in different ink and Desvaux’ writing on this label. The sheet contains two different plants: in the first place there is a leaf fragment with nine pairs of fertile pinnules, a black rachis and brown acicular hairs on the abaxial face of the costules. This is Cyathea grangaudiana from Mauritius and most likely does not correspond to the original material in Desvaux’ hands when describing Cyathea borbonica , because none of its particular features appear in his description. Secondly, there is a small sterile and glabrous fragment comprising four pinnae connected by a thin brown rachis probably from the apical part of a leaf. This fragment corresponds best to Desvaux’ description and is chosen here as the lectotype of Cyathea borbonica .

A photograph by Morton of a specimen consisting of four sterile pinnae, Commerson s.n. in P-JU! (Hb. Jussieu no. 1468) is filed as holotype of Cyathea borbonica in several herbaria (e.g., B!, BM!). Desvaux (1811) mentions that he consulted the collections of Jussieu and Lamarck. It is hence not improbable, that the fragment in his herbarium is originally from Jussieu’s herbarium. This not being explicitly mentioned in the protologue, a specimen from Desvaux’ own herbarium bearing the description in Desvaux’ writing should clearly be preferred in lectotypifying the name. Even though the specimen in Jussieu’s herbarium is morphologically completely identical to the lectotype here designated, it can only be called a putative isolectotype, because unnumbered sheets cannot be attributed with certainty to the same collection.

The leaf base with petiole scales and a description of the plant habit provide essential means of differentiating Cyathea borbonica var. borbonica from the Mauritius endemic Cyathea borbonica var. latifolia (Hook.) Bonap. and Cyathea borbonica var. sevathiana Th.Janssen & Rakotondr. Since the original material examined by Desvaux does not provide this information, we consider it necessary to designate an epitype to clarify the identity of Desvaux’ species.Taking into account the numerous misapplications of names in designating bipinnate taxa from the Mascarene islands (see below), this measure is likely to contribute towards stability in name usage.

Independently from Desvaux, the name Cyathea borbonica has been published by Poiret (1812: 425), clearly indicating a type, Bory s.n. in hb. Desfontaines (FI!). This name is a later homonym of Desvaux’ name. As it agrees morphologically with the type of Desvaux’ species, no replacement name is being proposed here for Poiret’s name. Later, Desvaux (1827: 322) writes: “2. Cyathea mascarena Sw., Mag. nat. ber., 1811, p. 328. Cyathea borbonica Poir. , enc. suppl., 2, p. 423”. The citation indicated for Cyathea mascarena refers to the protologue of Cyathea borbonica . Given that the name Cyathea borbonica does not appear in Desvaux (1827), and that the epithet mascarena does not appear in Desvaux’ article (1811: 328) nor in any of Swartz’ major works ( Swartz 1788, 1801, 1806) we interpret Cyathea mascarena “Sw. ” Desv. as a name intended by Desvaux to replace Cyathea borbonica Desv. in order to avoid homonymy with Poiret’s name. Although this replacement name was probably intended to preserve Poiret’s name, Cyathea mascarena “Sw. ” Desv. has to be regarded as a superfluous name and is thus illegitimate. It is unclear, for what reason Desvaux attributed this name to Swartz.

A multitude of varieties have been ascribed to this species. One, Cyathea borbonica Desv. var. latifolia (Hook.) Bonap. , is accepted in this treatment. Cyathea borbonica Desv. var. laevigata (Willd. ex Kaulf.) Bonap. , Cyathea borbonica Desv. var. madagascariensis (Kaulf.) Bonap. , and Cyathea borbonica Desv. var. pervilleana (Fée) C.Chr. are discussed below as doubtful species. Cyathea borbonica var. simulans (Baker) C.Chr. with adnate pinnules and densely paraphysate receptacles is a taxon from Madagascar, probably without affinity to the Mascarene species and will be dealt with in an upcoming treatment. The name Cyathea borbonica has been misapplied to a Madagascan tree fern ( Christensen 1932; Tardieu-Blot 1951) that is morphologically distinct from the Mascarene species (Janssen & Rakotondrainibe unpubl.).

2. Cyathea borbonica Desv. var. latifolia (Hook.) Bonap. ( Figs 2 ; 7E ; 8C )

Notes ptéridologiques 9: 48 (1920); Bonaparte, Notes ptéridologiques 16: 20 (1925), excl. specim. madag. — Cyathea canaliculata Willd. ex Spreng. var. latifolia Hook. , Species Filicum 1: 24, t. 13, f. A (1846). — Cyathea borbonica Desv. f. latifolia (Hook.) C.Chr., Dansk botanisk arkiv 7: 21 (1932); Tardieu in Humbert, Flore de Madagascar et des Comores, fam. 4: 13, f. 1, 8-9 (1951), excl. specim. madag. — Type: Mauritius, Sieber fl. mixt. exs.304 (lecto-, K!, here designated; isolecto-, B!, BM!, G!, P!); Black River gorges NP, Brise Fer Conservation Management Area, 5.IV.2005, Janssen et al. 2746 (epi-, P!, here designated; isoepi-, MAU!).

? Cyathea borbonica auct.: Bojer, Hortus Mauritianus:

388 (1837).

? Cyathea canaliculata auct.: Baker, Flora of Mauritius and

the Seychelles: 467 (1877).

ADDITIONAL MATERIAL EXAMINED. — Mauritius. Mare Longue, 13.II.1980, Benl et al. MR124 (M). — Boivin

s.n. (W). — Duncan s.n. (BM). — Mare Longue, 9.XII.1999, Florens & Sevathian 5 (MAU). — Kanaka Crater, 1982, Guého & Bosser s.n. (MAU). — Black River gorges NP, sur chemin 100 m avant Pigeon Wood Field Station, 20°26’22”S, 57°28’54”E, 707 m, 5.IV.2005, Janssen et al. 2743 (MAU, P). — Idem, Brise Fer Conservation Management Area, 5.IV.2005, Janssen et al. 2744 (MAU, P); 2747 (MAU, P). — Bassin Blanc, 6.VII.1979, Lorence et al. 2704 (K). — Curepipe, Rawson 21 (BM). — Sieber syn. fil. exs. 59 [?, specimen differs morphologically from all other Sieber syn. fil. exs. 59] (G). — Pouce Mt., 6.VIII.1983, Strahm s.n. (MAU). — Anon. s.n (B, K). — La Pouce, Anon. s.n. (K).

Without or with doubtful locality. Sieber 336 (P). — Anon. 6124 p.p. (P).

DESCRIPTION

Trunk: 2-5 m tall, diameter 6.5-9 cm, its surface dark brown, relatively sharply and densely muricate, a rudiment of the petiole bases persists in upper part of trunk, but is soon caducous exposing the leaf scars.

Leaf scars:3.5-6 × 1.5-2.5 cm, elliptical, displaying 3(-5) cavities on or below their lower rim.

Crown: usually umbrella-shaped, petioles and rachises arcuate, rarely petioles somewhat erect at their base, leaves spirally arranged in approximately five orthostichies forming more or less obvious pseudoverticils.

Trunk apex: hidden by close standing sigmoid petiole bases.

Petiole: 10-25 cm long, diameter 2.5-3 cm, its base rather strongly muricate, green to stramineous, abaxial face brown, rarely dark reddish brown on both faces, in young leaves with a tomentum of rapidly caducous brown squamules, at its base with distantly arranged brown aerophores on the entire abaxial face.

Lamina: bipinnate, widely elliptical, 150-220 cm long, 70-90 cm wide at its widest point (80-140 cm from base of lamina), bearing 27-35 pairs of alternate pinnae, basal pinnae gradually reduced in size, but rather widely spaced, slightly retroflexed and conduplicate, lamina subcoriaceous to coriaceous, pale green on abaxial face, shiny green on adaxial face, rachis coloured like petiole.

Largest pinnae: 30-42 cm long, spaced by 5- 6.5 cm, separate to slightly overlapping, costae

A

A’

A’

B

and costules stramineous, often tinged with red on abaxial face.

Largest pinnules: (3-)3.5-4 × 0.6-0.8 cm, sessile with an obtuse to truncate base, rarely auriculate, lanceolate to oblong, slightly falciform in their apical half, margin subentire, slightly revolute, rarely strongly and regularly crenate throughout, apex acute to obtuse, usually getting sharper from proximal to distal pinnules, with serrulate to crenulate margin, veins 1-2 furcate.

Scales and hairs: scales of the petiole base ascending up to 30 cm, more or less persistent, narrowly triangular, 3-4 × 0.2-0.3 cm, with long caudate twisted apex, shiny dark brown with a light brown (usually eroded) margin, spreading and with a tendency to agglutinate among themselves, but with their basal parts only, lateral scales usually shorter and with a broader base (usually about 0.3 cm), adaxial surface of costae and base of costulae with comparatively sparse, light brown, tortuous multicellular hairs, otherwise all axes glabrous except for scattered (often acaroid) squamules, adaxial face of rachis without hairs.

Sori: subcostular, separate to contiguous, covering entire pinnules (except their apex), but sometimes ascending only to 1/2, indusia globular, very thin and often inconspicuous, only a small collar-like rudiment around the base of the receptacle persists at maturity, receptacle capitate, with short inconspicuous paraphyses.

Spores: trilete, diameter (dehydrated) 50-60 µm, surface covered by slender rodlets.

DISTRIBUTION

Mauritius, endemic.

ECOLOGY 600-700 m. Middle elevation evergreen forest (“upland forest”). Inside the forest and on forest margins.

REMARKS

The plants are easily distinguishable in the field from Cyathea borbonica var. sevathiana and Cyathea borbonica var. borbonica by their stout habit with a usually umbrella-shaped crown and the strongly muricate trunk surface. In herbarium specimens, larger sized and more distant, more or less herbaceous pinnae and pinnules as well as larger, shiny brown scales are discriminative characters.

Pinna shape in this taxon is variable.It ranges from rather broad pinnules with acute apices ( Fig. 2 A’) to narrower pinnules with obtuse apices ( Fig.2A ), which may in rare cases be regularly crenate throughout ( Fig. 2A ”). The first condition appears to be usually associated with sterile material (cf. the isolectotype, Sieber fl. mixt. exs. 304, at P!) whereas the second condition is usually associated with fertile material (cf. the lectotype, Sieber fl. mixt. exs. 304, at K!, or the epitype Janssen et al. 2746, P!), although more material is needed to confirm this observation.

The specimen Janssen et al. 2744 (P, MAU) is morphologically distinct in having smaller pinnules, 2-2.3 × 0.6-0.7 cm, with a rounded apex. The specimen was taken from a young fertile plant found near a population of Cyathea borbonica var. latifolia in a shady forest habitat. The specimen is distinct from Cyathea borbonica var. sevathiana by its arching crown and the patent, herbaceous pinnules. Crown shape and the atropurpureous rachis differentiate the specimen from Cyathea borbonica var. borbonica from Réunion.

VERNACULAR NAME

Fandia.

TYPIFICATION AND SYNONYMY

The varietal type (K!) is a sheet containing a specimen (one detached pinna), Sieber fl. mixt. exs. 304, Mauritius, together with a specimen (two detached pinnae), Bojer s.n., “hab. in sylvis vastis insula Mauritii”, both collections being cited in the protologue. There is a second sheet, Bojer s.n. (K!), carrying a specimen identical to the Bojer collection on the first sheet. The first sheet, containing Bojer’s together with Sieber’s specimen, carries the following annotation by Holttum making reference to the two above-mentioned sheets and the illustration accompanying the protologue of Cyathea canaliculata var. latifolia Hook. : “The two Bojer specimens differ from the Sieber specimen in venation and indusia: t. XIIIA is mainly from Sieber, but shows some details from Bojer, 22.4.1980 ”. We agree with this statement adding that Cyathea borbonica var. latifolia exhibits considerable variability in pinnule shape ( Fig. 2 A-A”) and that both collections, Sieber fl. mixt. exs. 304 and Bojer s.n., can undoubtedly be regarded as being conspecific. We designate Sieber fl. mixt. exs. 304 the lectotype of the species following Holttum, who did not lectotypify but attached a holotype label to the Sieber specimen preferring it, as is also clear from his annotation, over the Bojer specimen.

Although the variety is rather well characterized by pinnule size, we chose to support the fragmentary type collection by designating an epitype providing scale characters and annotations concerning the plant habit in order to facilitate its separation from the other varieties of Cyathea borbonica .

The epithet latifolia, based on Hooker’s type, has been combined under Cyathea borbonica Desv. by Bonaparte (1920: 48; pro varietate), and Christensen (1932; pro forma). It has been applied by these authors and Tardieu-Blot (1951) to broad-leaved forms of a Madagascan tree fern with adnate pinnules that is most likely only distantly related to the Mascarene taxa (Janssen & Rakotondrainibe unpubl.).

3. Cyathea borbonica Desv. var. sevathiana Th.Janssen & Rakotondr. , var. nov. ( Fig. 3 )

A C. borbonicae Desv. var. borbonicae et a C. borbonicae var. latifoliae (Hook.) Bonap. differt pinnulis minoribus, 1.5-2(-2.8) cm longis, 0.4-0.5 cm latis, coriaceis, conduplicatis, apice rotundo, margine plus minusve revoluto; rhachi fere atropurpurea; trunco usque ad 1 m alto; corona infundibuliformi rhachibus rectis erectis pinnis pinnulisque conduplicatis; paleis basis petioli lucidis atro-castaneis, distortis, angustissimis.

TYPUS. — Mauritius. Black River gorges NP, Pétrin Field Station , 700 m, 5.IV.2005, Janssen et al. 2748 (holo-, P!; iso-, MAU!) .

ADDITIONAL MATERIAL EXAMINED. — Mauritius. NW of Mt. Cocotte, near waterfall, XI.1967, Barclay 437 (K). — Boivin s.n. (P). — Boivin s.n. (W [2]). — In sylvis, Bojer s.n. (BM, K, M). — Bojer s.n. (K, W). — Périer (Réserve), 15.IV.1974, Bosser 21867 (P). — Plaine Champagne, 4.VI.1976, Cadet 5496 (REU). — Lemann s.n. (BM). — Pétrin Nature Reserve, 14.XI.1975, Lorence 1492 (MAU). — Curepipe, 14.VII.1963, Rauh 10101 (BM). — Rivière Chevrettes, 17.X.1968, Vaughan s.n.

(MAU). — Anon. s.n. (MAU, W).

Without or with doubtful locality. Boivin s.n. (P). — Hooker s.n. (P). — Ins. Bourbonia [?], Lenorman s.n. (B). — Anon. s.n. (P).

DESCRIPTION

Trunk: up to 1 m tall, diameter 6-9 cm, its surface blackish, muricate, petiole bases persistent almost to the base, with their long sigmoid base appressed to the trunk and their apices spreading, but only persisting in rudiments at the base of the trunk.

Leaf scars: displaying three cavities on their lower rim.

Crown: funnel-shaped, with the petioles and rachises stiffly erect.

Trunk apex: hidden by close standing sigmoid petiole bases.

Petiole: 2-10 cm long, diameter 1.5-2 cm, usually atropurpureous, rarely light brown when dry.

Lamina: bipinnate, elliptic to oblanceolate, 125- 140 cm long, 45-70 cm wide at its widest point (75-80 cm from base of lamina), bearing 28-33 pinna pairs, basal pinnae gradually reduced in size, retroflexed and conduplicate, lamina coriaceous, pale green on abaxial face, shiny dark green on adaxial face, rachis coloured like petiole.

Largest pinnae: 17-25(-30) cm long, spaced by (2.5-) 3-4.5 cm, separate to slightly overlapping, all conduplicate, costae and costules stramineous, often tinged with red on abaxial face or completely atropurpureous, rarely light brown when dry.

Largest pinnules:1.5-2 × 0.4-0.5 cm, gap between adjacent pinnules equalling 1/2 to 1/1 their width, sessile with obtuse to truncate base, never auriculate, oblong, not markedly falciform (apex somewhat asymmetric), more or less strongly conduplicate, margin subentire, more or less strongly revolute, apex rounded to obtuse, with finely crenulate margin, veins 1-2-furcate.

Scales and hairs:scales of the petiole base ascending up to 20(-25) cm, persistent, very narrowly triangular, 2.5-3 × 0.1-0.2 cm, dull to shiny brown with a narrow light brown (usually eroded) margin, more or less appressed, but their slightly twisted apex usually spreading, adaxial surface of rachis and costae with comparatively sparse light brown, tortuous multicellular hairs, otherwise all axes glabrous except for scattered (often acaroid) squamules.

Sori: subcostular, appearing median in narrow pinnules with strongly revolute margin, separate to contiguous, covering entire pinnules (except their apex), but sometimes ascending only to 1/2, indusia globular, membranous, dehiscing in 2 or 3 lobes, receptacle capitate, with short inconspicuous paraphyses.

Spores: trilete, diameter (dehydrated) 50-60 µm, surface covered by slender rodlets.

DISTRIBUTION

Mauritius, endemic.

ECOLOGY

Around 700m. Forest margins and open,marshy habitats. Data were available for two specimens only.

REMARKS

This taxon can be distinguished from Cyathea borbonica var. borbonica and Cyathea borbonica var. latifolia by its smaller and coriaceous pinnules with usually rounded apices, and by its stiffly erect leaves with conduplicate pinnae and pinnules. Apart from characters observable in herbarium specimens, that are however mainly of quantitative nature, its particular habit in the field, which does not seem to be linked to specific ecological conditions makes this a distinctive taxon. Specimens of this variety have frequently been determined as Cyathea canaliculata or C. borbonica .

VERNACULAR NAME

Fandia.

ETYMOLOGY

The name of this variety has been chosen in honour of Jean-Claude Sevathian, field botanist in the service of Mauritian Wildlife Foundation who efficiently guided our fieldwork on Mauritius.

Figures

FIG. 1. — Cyathea borbonica Desv. var. borbonica: A, pinnules abaxially (sori partly omitted), detail of sori with acaroid squamules on costulae and appressed multicellular hairs on the veins of adaxial face of pinnule apices; B, two pinnae abaxially with part of rachis (sori partly omitted); C, habit; D, pinnules abaxially (sori partly omitted), form with rounded apices; E, scales from petiole base (left: three scales agglutinated with their bases; right: single scale); F, basal part of the leaf (petiole base up to first pinna pairs), lateral view; G, leaf scars. A, B, G, Janssen et al. 2697, P; C, uncollected, photograph at P; D-F, Janssen et al. 2670, P. Scale bars: A, D, E, G, 1 cm; A insets, 1 mm; B, F, 5 cm; C, 1 m.

FIG. 7. — Photographic documentation of field characters: habit (A-E), shoot apex (A’-E’), and trunk surface at breast height (A”- E”) are shown for each species; A-A”, Cyathea glauca Bory; B-B”, C. excelsa Sw.; C-C”, C. borbonica Desv. var. borbonica; D- D”, C. grangaudiana Th.Janssen & Rakotondr.; E-E”, C. borbonica var. latifolia (Hook.) Bonap. A, uncollected; A’, Janssen et al. 2728; A”, Janssen et al. 2686; B, B’, Janssen et al. 2700; B”, uncollected; C, uncollected; C’, Janssen et al. 2670; C”, Janssen et al. 2726; D, uncollected; D’, Janssen et al. 2738; D”, Janssen et al. 2740; E, E’, Janssen et al. 2746; E”, Janssen et al. 2743. Vouchers at P. Scale bars: A-E, 1 m; A’-E’, A”-E”, 10 cm.

FIG. 8. — SEM images of spores: A, Cyathea borbonica Desv.; B, C. grangaudiana Th.Janssen & Rakotondr.; C, C. borbonica var. latifolia (Hook.) Bonap.; D, C. excelsa Sw.; E, C. glauca; F, C. grangaudiana, sporangium (above) and sporangiaster with long apical hair (below), natural position in the sorus. A, Gaudichaud s.n., P; B, Bouton s.n., P; C, Janssen et al. 2747, P; D, Boivin s.n., P; E, Rakotondrainibe et al. 6913, P; F, Anon. 33 in hb. Doerfler, P. Scale bars: A-E, 10 µm; F, 100 µm.

FIG. 2. — Cyathea borbonica Desv. var. latifolia (Hook.) Bonap.: A-A’’, pinnules abaxially with part of costa (sori partly omitted), all drawings to same scale;A, common form with subcrenate margin and obtuse apices; A’, form with wide pinnules and acute apices; A’’, form with strongly crenate margins; B, habit; C, two pinnae abaxially with part of rachis (sori partly omitted); D, basal part of the leaf (petiole base up to seventh pinna pair), lateral view, one half of the petiole pruned away by longitudinal section; E, scales from petiole base (left: broad scale from lateral face; right: narrow scale from adaxial face); F, leaf scars. A, B, C, Janssen et al. 2746, P; A’, F, Janssen et al. 2743, P; A”, D, E, Janssen et al. 2747, P. Scale bars: A-A”, E, F, 1 cm; B, 1 m; C, D, 5 cm.

FIG. 3. — Cyathea borbonica Desv. var. sevathiana Th.Janssen & Rakotondr., var. nov.: A, pinnules abaxially with part of costa (sori partly omitted); B, habit; C, scale from petiole base; D, E, plants near the Pétrin Field Station, Black River gorges National Park, Mauritius. A-C, E, Janssen et al. 2748; D, uncollected. Scale bars: A, C, 1 cm; B, 1 m.