Terrestrials or epiphytes (non-Australian) with swollen fleshy stems bearing broad pleated leaves either grouped in the upper part of the stem or scattered along its length. Small flowers are borne on slender winged racemes which terminate a growth. Each flower has broad sepals, narrow petals and a broad labellum fixed to the base of the column. The unlobed labellum has 2 basal spur-like lobes which extend past the base of the column and a shallow sunken pit in front of the column. The labellum apex can be entire or often has a number of prominent teeth. The column is short without a column foot.
Significant Generic Characters
Terrestrial/epiphytic(non-Australian) orchids; roots thin, fleshy, unbranched; stems fleshy, resembling a pseudobulb, short to long, leafy when growing; leaves few-several per shoot, distal on the stem or scattered, plicate, thin-textured, non-articulate, petiolate; petiole channelled, basally sheathing the stem; inflorescence racemose, terminal, thin, multiflowered; peduncle winged; flowers non-resupinate, lasting few-several days, small, dull coloured, opening sequentially; sepals and petals free; petals narrower than the sepals; labellum sessile on the column, unlobed, broad, with 2 spur-like basal auricles; callus consisting of a shallow pit; column very short, without a foot; pollinia 4, in 2 pairs, without stalks.
Size and Distribution
A genus of about 320 species widely distributed in tropical regions of the world with a high degree of speciation in New Guinea. There are 5 endemic species in Australia restricted to tropical parts of Queensland, with 1 species also occurring in the Northern Territory. State occurrence: Queensland (including Moa Island), Northern Territory.
The native species of Crepidium range from the coastal lowlands to about 800 m alt. in the ranges and tablelands of northeastern Queensland. In Australia these orchids usually grow in soil and accumulations of litter in sheltered situations on the rainforest floor or near streams. In the tropics the climate has a dominant summer wet season (December to March) when the vast majority of rain falls, with the remaining months being much drier and having sporadic to intermittent rain.
Pollination: The native species of Crepidium have small flowers but they are apparently not self-pollinating. Capsules are produced sporadically and the flowers are believed to by splash-pollinated by raindrops dislodging the pollen from the anthers.
Reproduction: Reproduction in Crepidium is mainly from seed although occasionally aerial growths are produced from the upper nodes on a stem. Seed dispersal takes 6-10 weeks from pollination and the capsules develop in an erect position. Apomixis is unknown in the genus.
Seasonal Growth: Crepidium plants grow actively in spring, summer and autumn, some species becoming deciduous in winter and remaining dormant until spring when new shoots are produced (see also Notes).
Flowering: Flowering occurs mainly December to March but Crepidium lawleri flowers June to October.
Hybrids: Natural hybrids are unknown in these orchids.
The name Crepidium, which is derived from the Greek krepidion, little boot, is possibly based on the labellum shape.
Perennial, deciduous, terrestrial, lithophytic (non-Australian), rarely epiphytic (non-Australian) herbs (non Australian), sympodial. Plants glabrous, usually consisting of 2-few stems. Roots filamentous, thin, fleshy, unbranched, produced from the base of a shoot. Stems appearing pseudobulbous, fleshy, short to elongate, erect to procumbent. Pseudobulbs absent. Trichomes absent. Leaves plicate, convolute, lasting 1-3 seasons, scattered along the stem or confined to apical parts, non-articulate, often asymmetric, petiolate; petiole channelled, its base sheathing the stem. Venation parallel. Inflorescence racemose, many-flowered, erect, arcuate or pendulous, terminal, sometimes synanthous. Peduncle shorter, equal to or longer than the rhachis, alate, with scattered often retrorse sterile bracts. Rhachis shorter, equal to or longer than the peduncle, straight, alate, ribbed or grooved. Floral bracts small, narrow, partly sheathing. Pedicels short to vestigial, thin, merging with the ovary. Ovary short, straight, smooth. Flowers non-resupinate, tiny to small, dull coloured (green, yellow, red, brown or purple), shortly pedicellate. Perianth segments free, usually spreading. Dorsal sepal generally longer than the lateral sepals. Lateral sepals subsimilar to the dorsal sepal, generally smaller. Petals narrower than the sepals, entire. Labellum fixed by its base to the anterior column base, markedly dissimilar in size to the sepals and petals, ecalcarate. Labellum lamina unlobed, broad, with 2 basal spur-like auricles that extend backwards or downwards past the column, sometimes column-embracing; distal margins entire, dentate or lobed. Spur absent. Callus consisting of a shallow basal pit surrounded by a membrane. Nectar absent. Column very short, lacking free filament and style. Column foot absent. Pseudospur absent. Column wings relatively large, erect or projecting. Anther terminal, incumbent, shallowly concave, 2-celled, persistent, basifixed, smooth, erostrate. Pollinarium absent. Pollinia 4 in 2 pairs, clavate, yellow, hard, waxy, without caudicles. Viscidium absent. Rostellum small, transverse. Stigma entire, concave. Capsules dehiscent, glabrous, erect; peduncle not elongated in fruit; pedicels not elongated in fruit. Seeds numerous, light coloured, winged.
Crepidium has been included with Malaxis by many authors but can be distinguished by its above-ground stems, broad pleated leaves and unlobed labellum with prominent basal spur -like auricles. Crepidium can be distinguished from Dienia by its sessile labellum with prominent spur-like basal auricles and a shallow basal pit on the labellum, surrounded by a membrane.
Plants belonging to Crepidium subg. Crepidium have a similar growth habit whereby each stem grows for a season, loses its leaves, falls over and lies on the ground, remaining dormant for a short period during the dry winter season, after which a new shoot arises from a medial or basal node to produce the new seasons growth. Plants in Crepidium subg. Commelinoides are less seasonal with the stems remaining leafy, elongating over 2-3 seasons and new shoots arising from the medial or distal nodes.
1. Subgen. Crepidium. Leaves apical, lasting 1 season, labellum auricles produced backwards past the column, labellum apex with large teeth (C. fontinalis, C. flavovirens, C. lawleri, C. marsupichilum).
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