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Arthrochilus laevicallus

Arthrochilus laevicallus

Arthrochilus laevicallus Ormerod, Orchadian 16 (2011) 515 (-517; fig.

Type: L.J. Brass 8722 (holo AMES).


  • Drakaea irritabilis auct. non (F. Muell.) Rchb.f.: L.O. Williams, Bot. Mus. Leafl. Harv. Univ. 12 (1946) 152.

Terrestrial herb. Tuber oblongoid to ellipsoid, 0.6-0.8 by 0.3-0.45 cm. Leaves not seen. Inflorescence erect, glabrous, subterranean part 1-2.3 cm long, part above the ground 10.5-17.5 cm long; peduncle 7.5-13 cm long; sheathing scales 2-3, lax, 0.7-1.1 cm long; rachis laxly 4-7-flowered, 3.2-8.8 cm long; floral bracts ovate-lanceolate, 0,15-0.45 cm long, with acute apex. Pedicel and ovary club-shaped, 0.6-0.7 cm long, glabrous. Flowers not resupinate. Median sepal united dorsally to the column for 0.15 cm, ligulate-oblanceolate, 1.1 by 0.22 cm; apex truncate, near apex keeled; 5-nerved. Lateral sepals reflexed, falcate-ligulate, 0.85 by 0.2 cm; upper half with the midnerve much thickened and the inner margin folded in; upper half with the midnerve much thickened and the inner margin folded in; upper half with the midnerve much thickened and the inner margin folded in; apex truncate; 5-nerved. Petals reflexed, linear, subfalcate, 0.8 by 0.08 cm; apex subacute; 3-nerved. Lip hinged to apex of column foot; blade lanceolate-ligulate, in upper half (0.26 by 0.075 cm) decurved, in total 0.575-0.6 by c. 0.15 cm, with subacute apex; callus geniculate, its foot oblique and c. 0.15 cm long, knee covered in fleshy terete to clavate calli (distance between calli tips c. 0.13 cm), rest of callus parallel to lamina, tibiaeform, 0.31-0.32 cm long, median with scattered clavate calli, apex 3-lobulate, smooth, c. 0.1 mm wide. Column slender, curved, winged in the middle, on underside finely papillose-puberulous to the apex of the column foot, 0.87 cm long to tip of the anther; arms subfalcate, ligulate-lanceolate, subacute, c. 0.19 by 0.3 cm; column wings triangular, 0.28-0.3 by 0.26-0.27 cm, with uncinate apex; column foot at right angle to column, 0.29-0.3 cm by 0.13 cm.
(after Ormerod 2011)

Flowers green (but the callus on the labellum appears to be dark reddish).

Wet flats in savannah forest. Altitude not known, lowland.

Malesia (New Guinea, endemic)

Papua New Guinea (Western Province).

Warm growing terrestrial.


  • Family Orchidaceae
  • Subfamily Orchidoideae
  • Tribe Orchideae
  • Subtribe Thelymitrinae
  • Genus Arthrochilus
  • Species Arthrochilus laevicallus

Arthrochilus laevicallus differs from all 10 Australian species in the smooth apex of the labellum callus (not verrucose), a character unique in the genus.

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Arthrochilus laevicallus

Arthrochilus laevicallus Ormerod. Drawing by Paul Ormerod in Orchadian 16 (2011) 515 (-517; fig., based on the type, L.J. Brass 8722