Hybrid Butterfly Orchids
Epiphytes or lithophytes with indiscernible rhizomes anchored by roots that arise from nodes at the base of the pseudobulbs. The pseudobulbs are long, hard and cane-like, more or less cylindrical and leafy in the distal half to third. The leaves are relatively fleshy, flat, without any channel or groove, somewhat longer than wide, basally sheathing and with an entire apex. The flowers are borne on long racemes that arise from the upper nodes of a pseudobulb. They are very long-lasting and colourful with twisted sepals and petals The bases of the lateral sepals are fused with the column foot and the petals are much broader than the sepals. The labellum, which is distinctly 3-lobed, has fringed or crested central ridges and a long basal spur. It is stiffly attached to the apex of the column foot.
Similar Genera
Significant Generic Characters
Epiphytic/lithophytic orchids; rhizomes short, indiscernible; roots from basal pseudobulb nodes; pseudobulbs elongated, hard, cane-like, more or less cylindrical, leafy in the distal half to third; leaves relatively fleshy, flat, with an entire apex; racemes long, arising from distal nodes; flowers long-lasting, relatively large, colourful; perianth segments thin-textured, twisted; lateral sepal bases fused with the column foot; petals much broader than the sepals; labellum stiffly attached to the apex of the column foot; lamina 3-lobed, with a long basal spur; callus with fringed or crested central ridges; column foot with a deep central groove.
Size and Distribution
A hybrid genus that arises from natural hybridisation between species of Durabaculum and Vappodes, including backcrosses (Clements and Jones 2002). The genus, which occurs in northeastern Queensland, consists of 3 named hybrid taxa. State occurrence: Queensland (including Thursday and Little Woody Islands).
Ecology
XVappaculum hybrids occur in lowland and coastal areas growing on trees and rocks in moist or humid but airy sites that are often exposed to full sun. They grow in coastal scrubs, vine thickets, open forest, swamp forest and mangroves. 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 XVappaculum taxa last many days and are visited by large wasps and hornets which are capable of achieving pollination.
Reproduction: Reproduction in XVappaculum is mainly from seed, although plants can produce aerial growths. Seed dispersal takes 4-6 months after pollination and the capsules develop in a pendulous position. Apomixis is unknown.
Seasonal Growth: XVappaculum plants grow mainly during the spring, summer and autumn months and are relatively quiescent for the remainder of the year.
Flowering: Flowering occurs in summer, autumn and winter.
Hybrids: The flowers of XVappaculum taxa produce viable pollen and are capable of backcrossing and further hybridisation.
Derivation
XVappaculum is a combination of the parental generic names Vappodes and Durabaculum.
Botanical Description
Perennial, evergreen, epiphytic or lithophytic herbs, sympodial. Plants glabrous. Roots elongate, produced from nodes on the base of the pseudobulb. Rhizome superficial, branched. Pseudobulbs well-developed, crowded, elongate, cylindrical to ellipsoid, hard, when young covered by scarious bracts. Trichomes absent. Aerial growths often present, arising from the apical nodes on the pseudobulbs. Leaves lasting 1-3 seasons, distichous, occurring on the distal half to third of the pseudobulb, sessile, about as long as wide, flat, not grooved or channelled, thin textured but fleshy, smooth; base sheathing the pseudobulb; margins entire; apex entire. Inflorescence racemose, arcuate, arising from an apical or subapical node on a mature pseudobulb, multiflowered. Peduncle shorter or longer than the rhachis, the base covered with imbricate scarious bracts. Rhachis straight. Floral bracts scarious, sheathing the base of the pedicel. Pedicel relatively long, thin, merging with the ovary. Ovary short, straight, sometimes at right angles to the pedicel. Flowers resupinate, stalked, lasting many days, pink, mauve, purple or white; labellum with distinct striae. Perianth segments thin-textured, widely spreading, entire, straight, not twisted. Dorsal sepal free, subsimilar to the lateral sepals; apex entire, apiculate. Lateral sepals subsimilar to the dorsal sepal, attached by their bases to the column foot; apex apiculate. Petals free, much wider than the sepals; apex broadly obtuse, apiculate. Labellum stiffly attached to the apex of the column foot (see also spur below), markedly dissimilar in size and shape to the sepals and petals, calcarate. Labellum lamina more or less cuneate, strongly three-lobed; lateral lobes large, erect, flanking the column or incurved, entire; midlobe short or narrow, porrect to recurved; margins entire or undulate; apex entire. Callus consisting of narrow parallel ridges, usually fringed or crested on the midlobe. Nectar absent. Column lacking free filament and style, fleshy, shorter than the perianth segments, nearly straight. Column wings present, reduced, ventral and with short tooth-like apical stelidia. Column foot well developed, as long as or longer than the column, straight or curved, with a deep central groove. Spur present, formed by the fused elongated base of the labellum and apex of the column foot. Anther terminal, incumbent, 2-celled, persistent, attached dorsally by a ligulate claw, smooth, erostrate; apex papillate. Pollinarium absent. Pollinia 4 in 2 pairs, straight or falcate, yellow or orange, hard, waxy. Viscidium absent. Rostellum ventral, swollen, transverse. Stigma entire, transverse, concave. Capsules dehiscent, glabrous, pendulous; peduncle not elongated in fruit; pedicel not elongated in fruit. Seeds numerous, light coloured, winged.
Taxonomy
The taxa of this hybrid genus have features intermediate between the parents.
Notes
This group of hybrid taxa are very popular horticultural subjects in the tropics.
Nomenclature
XVappaculum M.A.Clem. and D.L.Jones, Orchadian 13(11): 492 (2002).
Type species: Dendrobium X superbiens Rchb.f. [XVappaculum superbiens (Rchb.f.) M.A.Clem. and D.L.Jones].
Dendrobium Sw. sect. Superbientia Kraenzl., Pflanzenr., Orch.-Mon.-Dend. VI: 257 (1910). Type species: Dendrobium X superbiens Rchb.f.
References
Clements, M.A. and Jones, D.L. (2002). Nomenclatural changes in the Dendrobieae (Orchidaceae), 1: The Australasian region. Orchadian 13(11): 485-497.
Dockrill, A.W. (1969). Australian Indigenous Orchids. Volume 1. The Society for Growing Australian Plants, Halstead Press, Sydney.
Dockrill, A.W. (1992). Australian Indigenous Orchids. Volume 1 & 2. Surrey Beatty & Sons in association with The Society for Growing Australian Plants, Chipping Norton, NSW.