AFRICAN

ORCHIDS

Gastrodia elatoides W.C.Huang, G.W.Hu & Q.F.Wang, Phytotaxa 349: 167 (2018).
Description:
Terrestrial, holomycotrophic herbs, ca. 70 cm tall. Rhizome tuberous, obconical-ellipsoid, ca. 9 cm long, 1.8 cm in diam., slightly flattened, nodes closely spaced with triangular scales, the upper part densely covered with lanate hairs. Raceme erect, peduncle ca. 60 cm tall, glabrous, brown to whitish, with 10 membranous sheaths; sheaths tubular, 8-10 mm long. Inflorescence with 32 flowers, rachis ca. 10 cm long; bracts triangular-ovate to triangular-lanceolate, 6-7 x 2-4 mm, nearly equal the length of pedicel plus ovary, dark greyish brown to dark brown, membranous, obviously trinerved, base surrounding the pedicel, apex acute. Pedicel white, ca. 3 mm long. Flower only opening slightly, resupinate, suberect; perianth tube urceolate with 4 ridges, base dilated towards the front, 8-9 x 5-7 mm, outer surface subglabrous, yellowish green, inside surface greyish green to light green; sepal lobes 3, broadly triangular-ovate, subequal, ca. 3 mm long, light green except yellowish green at apex, apex obtuse; petal lobes 2, broadly ovate to nearly round, base contracted, smaller than sepal lobes, ca. 2 mm long, yellowish green. Lip 6-7 x 3 mm, attached to the column foot, enclosed within perianth tube except for the apex; epichile trilobed, 4.0-4.5 x 3.0 mm, yellowish white, 2 lateral lobes erect, midlobe slightly decurved and yellow at apex, margin entire, apical half sparsely irregularly crisped; hypochile contracted into a claw, ca. 3 x 2 mm, middle part fused to the perianth tube, with a longitudinal keel in the middle, looking like an extension of the column foot, bilateral parts free, front half with a pair of gibbous folds, abaxial surface smooth, bluish green, adaxial surface bluish white, pruinose. Column straight, 7-8 mm long, with a tooth-like stelidium on each lateral side of the apex, stigmatic surface located at basal part with nectary, column foot short, ca. 1mm, fused on the perianth tube; rostellum well developed, 0.7 x 1.5 mm, anther hemispherical, ca. 1.5 mm in diam.; pollinia 2, granular, composed of friable massulae, without caudicles. Ovary obconical, ca. 3 mm long, verrucose, yellowish brown to dark brown. Fruits and seeds not seen.
Etymology:
Referring to the similarity of this species to G. elata.
Habitat:
The new species has only been found in North Madagascar in one rare population under rainforest trees in Montagne D’Ambre National Park. Gastrodia species are intricately linked to their habitat, owing to their specific mycorrhizal associations throughout their life cycle (Martos et al. 2009, Selosse et al. 2010, Martos et al. 2015). It is possible that G. elatoides occurs in adjacent areas that have not yet been fully explored.
Phenology:
Flowering in September.
Taxonomic notes:
Because the plant reaches 70 cm in height during flowering and possesses an urceolate perianth tube, Gastrodia elatoides should be included in Gastrodia section Gastrodia. It shows great similarity to Gastrodia elata in its triangular scales on a densely noded rhizome, height of peduncle, suberect and weakly opening flower, urceolate perianth tube with its base dilated towards the front and column elongate with the stigmatic surface located at basal part with the nectary and two tooth-like apical stelidia. However, the differences between them are also clear, including its triangular-ovate to triangular-lanceolate obviously trinerved bracts with the base surrounding the pedicel (vs. bracts oblong-lanceolate, veins not obvious and base not surrounding the pedicel in Gastrodia elata), apical margin of lip entire (vs. apical margin irregularly fimbriate in Gastrodia elata), epichile strongly trilobed (vs. epichile obscurely trilobed in Gastrodia elata), hypochile pruinose (vs. hypochile glabrous in Gastrodia elata) and ovary surface verrucose (vs. ovary surface smooth in Gastrodia elata).
Distribution:
Madagascar
References:
Gastrodia elatoides (Orchidaceae: Epidendroideae: Gastrodieae), a new holomycoheterotrophic orchid from Madagascar, Phytotaxa 349 (2): 167–172-2018