Cyathea excelsa Sw.

Janssen, Thomas & Rakotondrainibe, France, 2006, A revision of the fern family Cyatheaceae in the Mascarene Islands, Adansonia (3) 28 (2), pp. 213-241 : 227-231

5. Cyathea excelsa Sw. ( Figs 4 ; 7B ; 8D )

Journal für die Botanik (Schrader) 2: 93 (1800) ; Bojer , Hortus Mauritianus 388 (1837); Baker , Flora of Mauritius and the Seychelles 467 (1877); Cordemoy , Flore de l’île de La Réunion 39 (1895); Tardieu , Notulae Systematicae (Paris) 16: 156 (1960). — Alsophila celsa R.M.Tryon, Contributions from the Gray Herbarium 200: 30 (1970). — Type: ex insula Mauritii, Gröndal s.n. (lecto-, S! in hb. Swartz no. 3245, here designated; isolecto-, S!, UPS).

Cyathea canaliculata Willd. ex Spreng. , Systema Vegetabilium 4: 126 (1827); Kaulfuss , Enumeratio Filicum 260 (1824), nom. nud.; Bojer , Hortus Mauritianus 388 (1837); Baker , Flora of Mauritius and the Seychelles 466 (1877); Baker in Hooker & Baker, Synopsis Filicum , ed. 2, 23 (1883); Cordemoy, Flore de l’île de La Réunion 39 (1895). — Type: Habitat in insula Mauritii, A. du Petit-Thouars s.n. (holo-, B-W! no. 20184; iso-, P! in hb. Luerssen no. 11216, fragment).

ADDITIONAL MATERIAL EXAMINED. — Mauritius. Ayres s.n. p.p. (B). — Sentier Nord vers le bassin Blanc , 6.XII.1973, Badré 1089 (P). — Bois des parties élevées du Pouce, VIII.1849, Boivin s.n. (P). — Boivin s.n. (P). — In sylvis, Bojer s.n. (G). — In altis montibus, Bojer s.n. (K). — In sylvis in monte Pouce , Bojer s.n. (K). — Bojer s.n. (K, MAU). — Bordas s.n. (K, P). — Camp de Masque , Bory de St-Vincent s.n. (P). — Bory de St-Vincent 24 (B- W). — Bouron s.n. (B, P). — Duncan s.n. (BM). — Düring s.n. (B). — Gaudichaud s.n. (B). — Black River gorges NP, chemin vers mt Cocotte , 20°26’19”S, 57°28’27”E, 728 m, 4.IV.2005, Janssen et al. 2739 (MO, P). — Idem, Brise Fer Conservation Management Area , 5.IV.2005, Janssen et al. 2745 (MO, P). — Idem, Pigeon Wood Field Station , 20°26’22”S, 57°28’54”E, 707 m, 5.IV.2005, Janssen et al. 2749 (MO, P). — Montagne du Pouce, 7.VII.1887, Johnston s.n. (K). — Bassin Blanc crater, 25.X.1975, Lorence 1464 (MAU, P). — Shoulder of Pouce , 2.I.1865, Meller s.n. (MAU). — Néraud s.n. (G). — La Pouce, 13.VII.1963, Rauh 10086 (BM). — Curepipe, Rawson 24 (BM). — Richard s.n. (P [2]). — Sieber s.n. (BM). — La Hance Garden [?], Sieber syn. fil. exs. 58 (B, BM, G, K, P). — Sieber fl. mixt. exs. 303 (B, BM, G, P). — Telfaire s.n. (K). — Waglit s.n. (K). — Wallich 357 (BM). — Summit of the Pouce, VII.1858, Anon. s.n. (P). — Anon. s.n. (B [6], G, P). — Anon. 35 (P) .

Réunion. Sentier vers la Roche Écrite, forêt avant la plaine des Chicots , 25.XI.1973, Badré 1031 (P). — Same locality, 25.XI.1970, Barclay 2054 (K). — Baudouin 259 (P). — Bernier 22 (P). — Boivin s.n. (G, P). — Boivin 899 (B, G). — Forêt du quartier Moka, Bory de St-Vincent s.n. (P). — Bréon s.n. (P). — Carmichael s.n. (BM, K). — De Cordemoy s.n. (P [2]). — V.1875, de Cordemoy 14 (K). — De Cordemoy 157 (P). — Gaudichaud s.n. (G). — De l’Isle G 579 (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. 2700 (MO, P). — Le Maïdo , forêt de Maïdo, route forestière des Tamarins , au croisement avec le ravin Bras la Pompe , 21°04’27”S, 55°21’42”E, 1745 m, 1.IV.2005, Janssen et al. 2713 (MO, P). — Forêt de Bébour , sentier pédagogique de Bras Cabot, 21°07’30”S, 55°34’20”E, 1348 m, 2.IV.2005, Janssen et al. 2723 (P); 2737 (MO, P). — Forêt de Bébour, sentier de la rivière, 21°06”53’ S, 55°33”54’E, 1360 m, 2.IV.2005, Janssen et al. 2729 (P); 2730 (P). — Leprieur 83 (P). — Rawson 25 (BM). — Richard s.n. (P [2]). — Richard 239 (P). — Vieillard s.n. (B, P). — Bois des hauts de St-Paul, 2.VI.1882, Anon .

67 (P). — VI.1848, Anon. s.n. (P). — Anon. s.n. in hb. Maire (P). — Anon. s.n. (B, G, K).

Without or with doubtful locality. Bourbon ou Maurice, Boivin 899 (P). — Forster s.n. (UPS). — Anon. s.n. (K [2]). — Anon. 30 (BM [3]).

DESCRIPTION

Trunk: 2-5(-10) m tall, diameter 15-20 cm including the always persistent, strongly muricate, blackish to greyish brown dead petiole bases, that completely cover the trunk in apparently vertical rows, but are more or less eroded in the lower half of the trunk.

Crown: large, umbrella-shaped, with arcuate rachises.

Trunk apex: visible through the distant, straight to arcuate petiole bases, blunt, densely scaly.

Petiole: 10-40(-90) cm long, diameter 4-4.5 cm, coarsely and distantly muricate, green, abaxial face (reddish) brown, 1-2 subcontinuous line(s) of white aerophores on either side, occasionally a pair of pinnae of reduced size is found between the base and middle of the petiole.

Lamina: bipinnate-pinnatisect, elliptical, 200- 260 cm long, 110-160 cm wide at its widest point (110-120 cm from base of lamina), bearing 13-17 alternate pinna pairs, its base acute to obtuse, with pinnae rather abruptly reduced in size and usually increasingly spaced towards the base, basal pinnae more or less conduplicate, lamina herbaceous to subcoriaceous, more or less shiny green on both faces, rachis and costae smooth to finely muricate, glabrous, green to yellowish green, (reddish) brown on abaxial face.

Largest pinnae: 55-65 cm long, spaced by 10- 15 cm, separate to contiguous, widest in or below their middle.

Largest pinnules: 12-14 × 1.5-2.5 cm, contiguous to distant, sessile, basal pair of segments overlapping the costae, oblong, apex long caudate, pinnatisect with 3-4 mm wide adnate segments (the basalmost sessile), base of segments more or less broadened, proximally slightly decurrent, usually narrowly confluent at their bases, sinuses between adjacent segments more or less V-shaped, segments falciform, apex acute to obtuse, margin revolute and distantly serrulate to subentire in lower 2/3 of segment, flat and conspicuously serrulate in upper

A

B

C

1/3 of segment, veins 1-2-furcate, rarely more often in forms with strongly serrate margins.

Scales and hairs: scales of the petiole base ascending up to 15 cm, caducous, narrowly triangular, 3- 4.5 × 0.2-0.4 cm, twisted, dark brown, shiny, with narrow light brown toothed margin, spreading, petiole with brown caducous tomentum of short hairs and squamules, usually not dense, adaxial face of rachis and costae with dense, light brown, crispate antrorse multicellular hairs.

Sori: up to 5 pairs at the base of each segment, rarely covering entire segments and often confined to or even solitary at the base of the segments, contiguous, indusia globose, membranous, light brown, dehiscing irregularly in 2 or 3 lobes, receptacle capitate to short columnar, generally shorter than remnants of opened indusium, sporangia mixed with light brown to black sporangiasters consisting of a stalk composed by 3 or 4 rows of cells and a club-shaped head bearing a very short (1 or 2 cells) apical hair, sporangiasters are usually absent from specimens from Réunion which, in turn, exhibit short paraphyses among sporangia.

Spores: trilete, diameter (dehydrated) 30-40 µm, surface verrucose.

DISTRIBUTION

Mauritius, Réunion, endemic.

ECOLOGY

200-1700 m. Evergreen forest of various elevation although the species seems to prefer shaded habitats and is consequently rare in open vegetation of high altitudes.

REMARKS

The taxon is clearly distinct from all tripinnate taxa encountered in Madagascar and the Comoros by the cutting of its lamina in combination with globose indusia. On Réunion, Cyathea excelsa can be most easily distinguished from C. glauca by the slightly confluent pinnule segments with a serrulate apex in cases where the examination of the axial indument leaves any doubt. The receptacles of all specimens from Mauritius bear sporangiasters similar to those of Cyathea grangaudiana , although their head tends to be smaller and club-shaped bearing a shorter apical hair. Sporangiasters are present in about 16% of the collections from Réunion, provided the locality information on the labels can be trusted. These are all ancient and fragmentary collections and sporangiasters have not been observed during recent fieldwork in Cyathea excelsa from Réunion. The lectotype of C. excelsa and the holotype of C. canaliculata display black sporangiasters. As we can currently only hypothesize about the nature and origin of this structure, which appears to be largely endemic to Mauritius, we prefer not to recognize the specimens from Réunion lacking sporangiasters as a variety. A single fragmentary specimen with strongly crenate segments in their lower soriferous half and subentire acute apex as well as with cupshaped somewhat emarginate indusia from Réunion exists at P!, Anon. s.n. in hb. Maire. If the collection locality is correct, it is at present best to assign it to Cyathea excelsa , although with hesitation.

VERNACULAR NAMES

Fanjan femelle (apparently less frequently used than for Cyathea glauca ), fanjan, fandia.

TYPIFICATION AND SYNONYMY

In the Swartz herbarium at S three equivalent sheets of a collection by Gröndal s.n. from Mauritius are present, all corresponding to the protologue and carrying Swartz’ autograph. A holotype specimen is not obvious from Swartz’ annotations. We here designate the specimen with the registration number 3245 as the lectotype and consider the two other sheets (no. 3248 and no. 3307) as well as one sheet marked Gröndal at UPS as isolectotypes. Although the type is fragmentary, it is well distinguished from the other tripinnate species by the cutting of its lamina and its axial indument making the designation of an epitype unnecessary .

Kuhn (1868: 163) is the first to publish a reference to du Petit-Thouars s.n. in hb. Willdenow (B- W) no. 20184 as the type of Cyathea canaliculata Willd. ex Spreng. which is the only specimen we could trace bearing a description of the taxon in Willdenow’s hand. It consists of a single pinna without its adjacent rachis fragment. The name Cyathea canaliculata has been widely misapplied to designate virtually all, pinnate-pinnatisect to tripinnate, taxa of Cyatheaceae from the Mascarene islands (usually to the exception of Cyathea glauca Bory ). Willdenow’s original description of Cyathea canaliculata is glued on the cover of the type specimen in B-W!and has never been published: “ Cyathea canaliculata frondis triplicato-pinnatis, pinnulis ovato acuminatis, stipite canaliculato glabro canali villoso, caudice arboreo”. In contradiction to this, Sprengel (1827: 126) characterizes the species in his validating description by “fronde 2 pinnata”. Baker in Hooker & Baker (1883: 23) also describes the species as being “bipinnate” and confirms the confusion having arisen from the fragmentary type by remarking: “It is possible that this may have tripinnate fronds, but my numerous specimens are not large enough to indicate if it be so”.

Several authors ( Bojer 1837; Baker 1877; Cordemoy 1895; Tardieu-Blot 1960) cite Cyathea arborea (L.) Sm., Mémoires de l’Académie royale des Sciences (Turin) 5: 416 (1793), as a synonym of Cyathea excelsa following Bory (1804: 179), although it is not obvious from Bory’s text to which Mascarene tree fern species he refers. The neotropical Cyathea arborea is certainly distinct from all Mascarene species.

Figures

FIG. 4. — Cyathea excelsa Sw.: A, pinnule segments abaxially with part of costula (sori partly omitted); B, two pinnules abaxially with part of costa (sori partly omitted); C, habit; D, four sporangiasters from the receptacle; E, basal part of the leaf (petiole base up to first pinna), lateral view, one half of the petiole pruned away by longitudinal section, a pair of reduced pinnae is present at 14 cm from the petiole base; F, scale from petiole base. A-C, E, F, Janssen et al. 2749, P; D, Boivin s.n., P. Scale bars: A, 0.5 cm; B, F, 1 cm; C, 1 m; D, 200 µm; E, 5 cm.

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.