Cyathea glauca Bory

Janssen, Thomas & Rakotondrainibe, France, 2006, A revision of the fern family Cyatheaceae in the Mascarene Islands, Adansonia (3) 28 (2), pp. 213-241 : 231-234

6. Cyathea glauca Bory ( Figs 5 ; 7A ; 8E )

Voyage dans les quatre principales îles des mers d’Afrique 2: 206 (1804); Cordemoy, Flore de l’île de La Réunion 39 (1895); Tardieu, Notulae Systematicae (Paris) 16: 156 (1960). — Alsophila glaucifolia R.M.Tryon, Contributions from the Gray herbarium 200: 30 (1970). — Type: “Le plus bel arbre de la plaine des Osmondes, dans l’enclos du volcan”, Île des Mascareignes, Bory s.n. (holo-, P!; iso-, B-W! no. 20171; putative iso-, BM!).

ADDITIONAL MATERIAL EXAMINED. — Réunion. Sentier vers la Roche Écrite, forêt avant la plaine des Chicots, 25.XI.1973, Badré 1030 (P). — Balfour s.n. (B, K [2]). — Sentier de la Roche Écrite, 25.XI.1970, Barclay 2055 (K, MAU). — Baudouin 724 (P). — Plaine des Chicots, environs du gîte de la Roche Écrite, 25.IV.1980, Billiet et al. 836 (K). — Plaine des Palmistes, montée de la Plaine des Cafres, Le Boucan, VI.1851, Boivin s.n. (P). — Boivin s.n. (B, G, K, P [2]). — Bory de St-Vincent 23 (B-W). — Bory de St-Vincent 332 (P). — Brenner s.n. (P). — V.1875, de Cordemoy 19 (K). — De Cordemoy 136 (P). — Frappier s.n. (P). — Gaudichaud s.n. (G). — Geay s.n. (P). — Bélouve, 24.IX.1875, de l’Isle 578 (K, P). — Col de Bellevue, chemin vers Gros Piton Rond, 21°09’20”S, 55°35’54”E, 1425 m, 30.III.2005, Janssen et al. 2683 (MO, P). — Idem, colline à côté du parking au point culminant de la route nationale 3, 21°09’20”S, 55°35’54”E, 1433 m, 30.III.2005, Janssen et al.2686 (MO, P). — Le Maïdo, route du Maïdo, à 2 km du sommet, 21°03’42”S, 55°22’46”E, 1965 m, 1.IV.2005, Janssen et al. 2709 (P); 2710 (MO, P). — Same locality, 1976 m, Janssen et al. 2711 (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. 2715 (P); 2721 (MO, P); 2722 (P). — Forêt de Bébour, sentier de la rivière, 21°06’53”S, 55°33’54”E, 1360 m, 2.IV.2005, Janssen et al. 2727 (MO, P, REU); 2728 (P). — St-Denis, RN Roche Écrite, sentier menant du parking à la fin de la route forestière de la Roche Écrite vers la plaine des Chicots, 20°57’30”S, 55°26’21”E, 1335-1918 m, 7.IV.2005, Janssen et al. 2751 (MO, P); 2752 (MO, P). — Idem, juste en dessous du gîte d’étape de l’ONF, 20°59’06”S, 55°26’44”E, 1810 m, 7.IV.2005, Janssen et al. 2753 (MO, P). — Plaine des Cafres, au Piton Desforges, 9.XII.1969, Onraedt R116 (K). — Piton de la Mare à Boue, Plaine des Cafres, à 2 km à l’ouest du col de Bellevue, 6.XI.2004, Rakotondrainibe et al. 6918 (P). — Forêt de Bébour, col de Bébour, 5.XI.2004, Rakotondrainibe et al. 6913 (P). — Bélouve, 19.IX.1882, Anon. s.n. (P). — Anon. s.n. in hb. Vilmorin (P). — Anon. s.n. (P).

DESCRIPTION

Trunk: 1-5 m tall, diameter (9-) 10-14 cm (up to 17 cm including the occasionally persistent petiole bases), its surface brown to greyish, muricate, more or less rudimentary scaly, petiole bases usually only persistent in upper part of the trunk, more or less rapidly caducous and exposing the leaf scars, trunk frequently with short ramifications near its apex.

Leaf scars:3.5-7.5 × 3.5-4.5 cm, elliptic to distincly rhombiform, rather close standing, with several shallow cavities on lower rim and below.

Crown: rather variable in size, more or less umbrella-shaped with long arching to rather straight and short petioles and rachises, leaves spirally arranged in approximately six orthostichies.

Trunk apex: visible through the distant arcuate to sigmoid petiole bases, blunt, densely scaly, occasionally obscured by pinnae of reduced size crowded at the petiole bases.

Petiole: (25-)50-100(-120) cm long, diameter 3.5-4 cm, sparsely muricate, stramineous to green, abaxial face castaneous to dark brown, one row of white to dark brown 0.5-1.5 cm long aerophores on either side, a pair of pinnae of reduced size (about 15-30 cm long) occasionally inserted at about 10- 20 cm from the base of the petiole.

Lamina: bipinnate-pinnatisect, ovate to elliptical, 140-220(-270) cm long, (85-) 110-140 cm wide at its widest point (70-80[-120] cm from base of lamina), bearing 12-17 alternate pinna pairs, its base more or less truncate, basal pinnae frequently conduplicate and more or less retroflexed, lamina coriaceous, abaxial face glaucous to pale green, adaxial face shiny bright to dark green, rachis and costae smooth, coloured like the petiole.

Largest pinnae: 48-65 cm long, spaced by 8- 12(-15) cm, oblong.

Largest pinnules: 8-10 × 1.5-2 cm, sessile, separate to overlapping, frequently slightly conduplicate, apex acute to shortly caudate, pinnatisect with 2-3 mm wide adnate segments, not widened (occasionally even tapered) towards their base, always clearly separated by a short stretch of the costula, basally confluent towards the pinnule apex, segment apices obtuse to rounded, falciform, with subentire to sinuate, revolute margins, veins once furcate, segments occasionally conduplicate, the basalmost segments of each pinnule sessile to petiolulate, overlapping the costa, and frequently with crenate margins.

Scales and hairs: scales of the petiole base caducous, narrowly triangular, 3-4.5 × 0.2-0.3 cm, with twisted and crispate, long caudate apex, brown, shiny, with narrow light brown ciliate (but often eroded) margin, petiole, rachis, and costae tomentose, bearing orange to light brown intricate, highly branched and crispate multicellular hairs, costulae less densely hairy, adaxial face of rachis and costae (less frequently also costulae) with ciliate-dentate triangular to lanceolate light brown membranous scales, these scales sparse on the abaxial face of the respective axes.

Sori: 1-5 pairs per segment, covering up to 2/3 of the segment, indusia globose, dehiscing in 2 or 3 lobes, receptacle capitate, shorter than rim of opened indusia.

Spores: trilete, diameter (dehydrated) 35-45 µm, surface finely verrucose.

DISTRIBUTION

Réunion, endemic.

ECOLOGY

1300-2000 m. Inside evergreen forest and (more frequently) on crests and slopes amidst low shrubby vegetation.

REMARKS

The taxon is clearly distinct from all Madagascan tripinnate taxa by its tomentum. Because of an occasionally sparse tomentum, the subconfluent segment bases, and a weakly developed colouring of the abaxial lamina surface, it is often impossible to unambiguously distinguish juvenile plants of Cyathea glauca from C. excelsa . The habit of C. glauca is rather variable. Plants in altitudinal, rather exposed habitats have smaller leaves and crowns, frequently subapically branched trunks, quickly decaying dead petiole bases that soon leave the leaf scars exposed, short petioles, stiff rachises, and a very dense axial tomentum as opposed to forms of lower altitude forest habitats with larger leaves and crowns, simple trunks that usually remain covered with dead petiole bases throughout, long and arched petioles, and a less dense tomentum. However, intermediate forms occur and the variation observed being most probably due to ecological conditions does not merit formal taxonomic recognition. Bory 332, Janssen et al. 2752, and Anon. s.n. in hb. Vilmorin (all at P) are distinct by their bigger pinnules (up to 12 × 2.5 cm) with strongly crenate segments. However, intermediate forms occur and this character is in our opinion too variable to justify formal description. According to Badré & Cadet (1978), the leaves of Cyathea glauca dry up and are regenerated with annual periodicity during the hot and humid season.

VERNACULAR NAMES

Fanjan femelle (with reference to the trunk base being occasionally widened by adventitious roots), fanjan bleu (fide Cordemoy 1895), fanjan.

TYPIFICATION

A specimen consisting of one detached pinna, morphologically completely identical to the holotype (P!), exists in B-W!(no. 20171) bearing the number “23” and being linked to the original material by the remark “envoi à Willdenow sous le no. 23” in

D

Bory’s hand on the holotype specimen. It is hence an isotype. A morphologically identical fragment collected by Bory in 1803, but without number is present at BM! and considered to be a putative isotype. Although fragmentary, Bory’s type collection cannot be confounded with any of the species from the region making epitypification unnecessary.

Figures

FIG. 5. — Cyathea glauca Bory: A, strongly crenate form, pinnule segments abaxially with part of costula; B, two pinnules abaxially with part of costa (sori partly omitted); C, pinnule segments abaxially with part of costula;D, habit (left:plant from open habitat on a mountain ridge;right:plant from understorey rainforest habitat); E, a single highly branched tortuous hair from the tomentum covering all major axes (arrow: point of attachment); F, scale from abaxial face of costula; G, leaf scar; H, 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 13 cm from the petiole base; I, scale from petiole base.A, Anon.s.n. in hb. Vilmorin,P; B, C,G-I, Janssen et al. 2686, P; D,left, uncollected, photograph at P; D, right, Janssen et al. 2727, P; E, F, Janssen et al. 2683, P. Scale bars: A, B, G, I, 1 cm; C, 0.5 cm; D, 1 m; E, 100 µm; F, 500 µm; H, 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.