Mica Orchid
Evergreen epiphyte reproducing solely from seed. Plants have barely discernible thin short-creeping branched rhizomes anchored by filamentous roots that arise from nodes along the rhizome. The pseudobulb and leaf are fused together to form a single unit, these combined leaf-like structures being closely spaced and arranged alternately along the rhizomes. Each leaf-like structure is longer than wide, thick, fleshy, broadly grooved and with a pitted surface. The stalkless flowers are borne singly and break through the leaf surface at the base of the broad groove. They are relatively small, thin-textured, with no apparent scent and each lasts a few days. The bases of the lateral sepal are fused with the column foot and with each other for a short distance in front and the petals are smaller than the sepals. The labellum, which is stiffly hinged to the apex of the column foot, is very obscurely three-lobed and has a thick fleshy mid-lobe with papillate margins.
Similar Genera
Significant Generic Characters
Epiphytic/lithophytic habit; thin rhizomes; filamentous roots; pseudobulb and leaf fused to form a single leaf-like structure; leaf-like structure lasting several seasons, broadly grooved and pustulate; flowers sessile, breaking through the base of the leaf; labellum obscurely three-lobed; proximal part thin-textured, with papillate margins; midlobe fleshy.
Size and Distribution
A monospecific genus with the single species, Stilbophyllum toressae, endemic in northeastern Queensland between Mt Finnigan (15°50' S) and the Cardwell Range (17°55' S), where it is distributed from the lowlands to highland regions at about 2000 m alt.
Ecology
Stilbophyllum toressae grows on trees or rocks in rainforest and in moist or humid areas of open forest, especially where there is abundant air movement. The climate is tropical and the majority of rain falls during the summer wet season (December to March), with the remaining months much drier and having sporadic or intermittent rain.
Biology
Pollination: The flowers of Stilbophyllum toressae last for a few days, are musk-scented and are pollinated on warm days by small native bees of the genus Trigona (Bartareau 1994).
Reproduction: Reproduction in Stilbophyllum toressae is solely from seed. Seed dispersal takes 4-6 months after pollination and the capsules, which are sessile in the base of the leaf, develop in an erect position. Apomixis is unknown in the genus.
Seasonal Growth: The plants grow during the summer months and for a period after the wet season and are relatively quiescent for the remainder of the year.
Flowering: Flowering occurs sporadically throughout the year.
Hybrids: Natural hybrids involving Stilbophyllum toressae are unknown.
Derivation
The generic name Stilbophyllum is derived from the Greek stilbos, glitter, shine and phyllon, leaf. The leaves have a glistening, mica-like appearance.
Botanical Description
Perennial, evergreen, epiphytic or lithophytic herbs, sympodial. Plants glabrous except for papillae on the labellum. Roots filamentous, produced singly from nodes along the rhizome. Rhizomes closely appressed to the host, barely discernible, creeping, branched, covered by closely sheathing, imbricate, scarious bracts. Pseudobulb appearing absent, actually fused with the leaf to form a single composite, leaf-like unit, when young covered by scarious bracts. Trichomes absent. Leaf-like unit sessile, not sheathing at the base, longer than wide, broadly grooved, pustulate or pitted, thick and fleshy, coriaceous; apex entire. Inflorescence arising from the apex of the pseudobulb and bursting through the leaf at the base of the ventral groove, 1-flowered. Peduncle absent. Floral bract scarious, sheathing the base of the ovary. Pedicel absent. Ovary short, straight, smooth. Flowers resupinate, sessile, lasting a few days, cream. Perianth segments thin-textured, spreading. Dorsal sepal free, smaller than the lateral sepals; apex entire, flat. Lateral sepals mostly free, larger then the dorsal sepal, attached by their bases to the column foot and fused for a short distance in front of the column foot; apex entire. Petals free, smaller than the sepals; apex entire. Labellum stiffly hinged to the apex of the column foot, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina more or less oblong, very obscurely three-lobed; proximal two-thirds thin-textured, flat, with thickened papillate margins; mid-lobe thick and fleshy, yellow, colluviate; apex entire. Callus obscure. Nectar absent, although distal parts of the column foot appear shiny. Spur absent. Column lacking free filament and style, short, nearly straight. Column wings present, ventral and with short tooth-like apical stelidia. Column foot well developed, curved. Pseudospur formed by the bases of the lateral sepals and the column foot. Anther terminal, incumbent, 2-celled, persistent, attached dorsally by a ligulate claw, smooth, erostrate, with an anterior papillate fringe. Pollinarium absent. Pollinia 4 in 2 pairs, falcate, yellow or orange, hard, waxy. Viscidium absent. Rostellum ventral, transverse. Stigma entire, transverse, concave. Capsules sessile dehiscent, glabrous, erect; peduncle not elongated in fruit; pedicel not elongated in fruit. Seeds numerous, light coloured, winged.
Nomenclature
Stilbophyllum D.L. Jones and M.A.Clem., Orchadian 13(11): 490 (2002).
Type species: Bulbophyllum toressae F.M.Bailey.
References
Clements, M.A. and Jones, D.L. (2002). Nomenclatural changes in the Australian and New Zealand Bulbophyllinae and Eriinae (Orchidaceae). Orchadian 13(11): 498-501.
Bartareau, T. (1994). The reproductive ecology of Dendrobium toressae (Bailey) Dockr., a geographically restricted species in north-east Queensland. Orchadian 11(3): 106-112.