Snake orchids
Epiphytes or lithophytes with thin creeping branched rhizomes appressed to the host and anchored by short filamentous roots arising from nodes on the rhizomes. The small, single-noded pseudobulbs are widely spaced on the rhizomes, each with a single, smallish, terminal, flat, thin-textured leaf that ranges from longer than wide to about as wide as long. The flowers, borne singly on thin wiry inflorescences that arise from nodes along the rhizome, are small, thin-textured, last from a few hours to a few days and are porrect to nodding with no noticeable scent. The petals are smaller than the sepals and the labellum, which is 3-lobed and fleshy, is firmly hinged to the apex of the column foot.
Significant Generic Characters
Epiphytic/lithophytic orchids; plants appressed; roots filamentous, short; rhizomes thin, long-creeping, branched; pseudobulbs small, single-noded, widely spaced; leaf single, smallish, thin-textured; inflorescence thin, wiry, arising from rhizome nodes; flowers single, small, thin-textured; petals smaller than the sepals; labellum firmly hinged to the apex of the column foot; labellum lamina three-lobed, fleshy.
Size and Distribution
A genus of 4-5 species, 3-4 endemic in northeastern Queensland and a single species endemic in New Caledonia. State occurrence: Queensland.
Ecology
In Australia species of Serpenticaulis are confined to the tropics. They grow in rainforest and humid areas of open forest on trees or rocks in situations ranging from shade to moderately bright light, where the humidity is generally high, and with free air movement. They are distributed over a wide altitudinal range and are often common at moderate to high altitudes in the ranges and tablelands.
Biology
Pollination: The flowers of species of Serpenticaulis last from a few hours to 2-4 days and are insect-pollinated, the vectors apparently being small flies that feed on nectar produced by the labellum.
Reproduction: Reproduction in Serpenticaulis is solely from seed. Seed dispersal takes 2-4 months after pollination and the capsules develop in an erect position. There is no increase in the length or thickness of the peduncle or pedicel during this process. Apomixis is unknown in the genus.
Seasonal Growth: The plants grow strongly in the spring and summer months and are relatively quiescent for the remainder of the year.
Flowering: Flowering occurs sporadically throughout the year.
Hybrids: Natural hybrids involving species of Serpenticaulis are unknown.
Derivation
The generic name Serpenticaulis is derived from the Latin serpentis, snake and caulis, stem, in reference to the long-creeping rhizomes.
Botanical Description
Perennial, evergreen, epilithic herbs, sympodial. Roots filamentous, produced from nodes on the rhizome. Rhizomes appressed to the host, thin, creeping, much branched, with closely sheathing, imbricate, scarious bracts. Pseudobulbs appressed to the rhizome, in-line, single-noded, moderately to widely spaced, small, ovoid, smooth or ribbed. Trichomes absent. Leaves sessile to subsessile, 1- per shoot, terminal on a pseudobulb, not sheathing at the base, flat, from longer than wide to about as wide as long, smooth, firm-textured, coriaceous; apex unequal, entire or notched, flat. Inflorescence arising from the stem, 1-flowered, erect. Peduncle longer than the pedicel or subsimilar, thin and wiry, with 1-2 tubular, closely sheathing to spreading, scarious sterile bracts. Floral bracts tubular, sheathing, membranous. Pedicel shorter than the peduncle or subsimilar, thin, straight or curved, smooth. Ovary short, straight, merging with the pedicel, smooth or wrinkled. Flowers resupinate, pedicellate, porrect to nodding, lasting from a few hours to a few days, dull coloured (cream, yellow or red, sometimes striped with red), unscented. Perianth segments thin-textured, spreading to incurved. Dorsal sepal free, similar or dissimilar to the lateral sepals; apex flat or cymbiform. Lateral sepals similar or dissimilar to the dorsal sepal, attached by their bases to the column foot; apex flat or cymbiform. Petals free, much smaller than the sepals, entire. Labellum hinged by a short claw to the apex of the column foot, firmly attached, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina more or less ligulate, obscurely three-lobed, thick and fleshy, curved; lateral lobes basal, suberect; margins entire; apex entire. Callus obscure, consisting of a shallow basal channel. Nectar present. Column lacking free filament and style, short, straight. Column wings present, ventral, and with elongate apical stelidia. Column foot well developed, curved upwards and sometimes thickened at the apex. Anther terminal, incumbent, 2-celled, persistent, hinged, smooth or papillate, rostrate. Pollinarium absent. Pollinia 4 in 2 pairs, crescentic, yellow or orange, hard, waxy. Viscidium absent. Rostellum ventral, transverse. Stigma entire, transverse, concave. Capsules small, dehiscent, glabrous, erect; peduncle not elongated in fruit; pedicels not elongated in fruit. Seeds numerous, light coloured, winged.
Taxonomy
Serpenticaulis is a recently erected genus (Clements and Jones 2002) to cater for a small group of species with long-creeping rhizomes and widely spaced pseudobulbs. Some authors, such as Dockrill (1992), have included these orchids in Bulbophyllum section Micromonanthe Schltr, however Schlechter (see 1982 translation) clearly states that members of section Micromonanthe have a caespitose habit with crowded pseudobulbs.
Nomenclature
Serpenticaulis M.A.Clem. and D.L.Jones, Orchadian 13(11): 500 (2002).
Type species: Serpenticaulis bowkettiae (F.M.Bailey) M.A.Clem. and D.L.Jones
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.
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.
Schlechter, R. (1982). The Orchidaceae of German New Guinea (English translation by R.S. Rogers, H.J. Katz and J.T. Simmons). Australian Orchid Foundation, Melbourne.