Creeping Burr Orchid
Epiphytes or lithophytes. Rhizome short but well developed, anchored by thin, branched roots that arise from basal nodes. Pseudobulbs present, moderately spaced, hard, short. Leaf solitary, from the apex of a pseudobulb, sessile, thick-textured, longer than wide or of similar width and length, flat, with an unequally notched apex. Flowers produced singly from two meristems, one in the leaf axil and the other behind the leaf. Each flower lasts 2-5 days, is supported by a short peduncle with an apical abscission zone between it and the pedicel, and has relatively thick-textured flat segments. Dorsal sepal similar to the lateral sepals. Lateral sepal bases partly fused with each other and with the column foot and basal margins of the labellum. Petals much narrower than the sepals. Labellum firmly attached to the apex of the column foot and partly to its margins to form a short pseudospur. Labellum lamina distinctly three-lobed; lateral lobes small; mid-lobe thickened. Callus consisting of a simple hairy plate.
Similar Genera
Significant Generic Characters
Epiphytic or lithophytic habit; rhizome creeping; pseudobulbs present; leaves lasting several seasons, solitary on a pseudobulb; two floral meristems present on each growth, one in the leaf axil and the other behind the leaf; flowers produced singly at sporadic intervals; labellum unlobed.
Size and Distribution
A small genus of 9 species occurring in New Guinea, Indonesia, Moluccas and Borneo with a single non-endemic species , Sarcocadetia wariana, in northern Queensland where it occurs in some islands of Torres Strait and the Iron Range (12°36' S) and McIlwraith Range (13°46' S) on Cape York Peninsula. State occurrence: Queensland (including Moa Island).
Ecology
Sarcocadetia wariana grows on trees and rocks in rainforest and moist sites, such as sheltered slopes and the beds of streams or along their banks. The plants mainly occur in lowland situations and at low to moderate altitudes in the ranges. The prevailing climate is tropical with the majority of rain falling during the summer wet season (December to March) and the remaining months being much drier.
Biology
Pollination: The flowers of Sarcocadetia wariana last for 3-5 days and are insect-pollinated but the vector is unknown.
Reproduction: Reproduction in Sarcocadetia is solely from seed. Seed dispersal occurs 4-6 months after pollination and the capsules develop in a nodding position. Apomixis is unknown in the genus.
Seasonal Growth: The plants grow actively during the spring and summer months and are relatively quiescent for the remainder of the year.
Flowering: Flowering occurs in spasmodic bursts between autumn and spring.
Hybrids: Natural hybrids, either interspecific or intergeneric, involving species of Sarcocadetia are unknown.
Derivation
The name Sarcocadetia refers to the fleshy nature of these plants (Greek sarcos, fleshy) and their relationship with the genus Cadetia.
Botanical Description
Perennial, evergreen, epilithic herbs, sympodial. Roots elongate, branched, filamentous, produced from nodes on the rhizome. Rhizome short. Pseudobulbs well developed, moderately crowded, hard, short, 1-noded, when young covered by scarious bracts. Trichomes present on the column and labellum. Aerial growths absent. Leaves solitary on a pseudobulb, sessile or shortly petiolate, longer than wide or of similar length and width, thick-textured, fleshy, smooth, flat or channelled, base not sheathing; margins entire; apex unequally emarginate. Inflorescence single-flowered, arising from two meristems, one in the leaf axil, the other behind the leaf; each meristem produces a single flower in its lifetime. Peduncle short, with an apical abscission zone at the base of the pedicel. Floral bracts scarious, persistent, sheathing the peduncle. Pedicel short, thin, fleshy, merging with the ovary. Ovary short, straight or curved, porrect from the pedicel, glabrous. Flowers non-resupinate, stalked, lasting 2-5 days, white or cream with yellow in the labellum. Perianth segments thin-to firm-textured, widely spreading, entire, flat. Dorsal sepal free, subsimilar to the lateral sepals, straight; apex entire, flat. Lateral sepals subsimilar to the dorsal sepal, widely spreading, straight, partly fused with each other and attached by their broad bases to the column foot; apex entire. Petals free, of similar length to the sepals but much narrower; apex entire. Labellum stiffly attached to the apex of the column foot, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina firm-textured, unlobed; basal part narrow, thin textured; distal part well-developed thickened, porrect, shortly hairy. Spur absent. Callus consisting of a simple hairy plate. Nectar present. Column lacking free filament and style, fleshy, shorter than the perianth segments, nearly straight, anteriorly hairy. Column wings present, well developed, ventral, with extended, tooth-like, apical stelidia higher than the anther. Column foot well developed, as long as the column, in line with it, nearly straight. Pseudospur present, formed by the union of the anterior basal margins of the lateral sepals, the bases of the lateral sepals with the margins of the column foot and the basal margins of the labellum. Anther terminal, incumbent, 2-celled, persistent, attached dorsally by a ligulate claw, smooth, rostrate; apex smooth. Pollinarium absent. Pollinia 4 in 2 pairs, straight or slightly falcate, yellow or orange, hard, waxy. Viscidium absent. Rostellum ventral, broad. Stigma bilobed, concave. Capsules dehiscent, glabrous, cernuous; peduncle not elongated in fruit; pedicel not elongated in fruit. Seeds numerous, light coloured, winged.
Taxonomy
Within the Dendrobieae, Sarcocadetia is distinguished by single-noded pseudobulbs, single terminal leaf and 2 floral meristems, one in the leaf axil, the other behind the leaf, each meristem capable of producing only a single flower in its lifetime. Sarcocadetia can be distinguished from Cadetia by its creeping habit, short fleshy single-noded pseudobulbs, fleshy leaves and 2 floral meristems per shoot each only producing a single flower.
Nomenclature
Sarcocadetia (Schltr.) M.A.Clem. and D.L.Jones Orchadian 13(11): 490 (2002).
Type species: Cadetia funiformis (Blume) Schltr. [Sarcocadetia funiformis (Blume) M.A.Clem. and D.L.Jones].
Infrageneric Taxa: No infrageneric taxa are currently recognised.
References
Clements, M.A. and Jones, D.L. (2002). Nomenclatural changes in the Dendrobieae (Orchidaceae) 1: The Australasian region. Orchadian 13(11): 485-497.