Citation: D. Jones & M. Clements, sp. nov.1

Synonymy: Diplodium dolichochilum, Pterostylis alata

Common name: Mallee green-hood.

Description:
Plant slender, 8-20 cm high; a small rosette of 3-6 ovate leaves on long peduncles in non-flowering plants; cauline leaves lanceolate, 2-5 cm x 3-6 ram, the larger ones above.

Flower single, maroon or brownish and white, striated; galea 25-35 mm long, firstly erect, gradually incurved, apex blunt, dorsal sepal blunt or shortly acuminate; petals blunt; lateral sepals (lower lip) erect, the lobes separated by a narrow to broad sinus notched at the middle, not bulging, the tips produced into long curved filiform points embracing the galea and greatly exceeding it; labellum on a movable claw, lamina lanceolate, c. 8 mm long, 1-1.2 mm broad, dark-green or brown, thin-textured; tip acuminate, decurved and protruding through the sinus of the lower lip, central keel not very distinct; basal appendages linear, curved, penicillate; column erect, winged, upper tip of the wings falcate, acute, lower lobe oblong, blunt with inturned ciliate margins; stigma prominent, 2-lobed, elliptic, centrally located on the column.

Published illustration: Fiveash & Lothian 1974) Australian orchids, pl. 59.

Distribution:  Forms extensive colonies on limestone or in calcareous sands in mallee or mallee heathland in areas receiving 300-500 mm annual rainfall. S.Aust.: FR, EP, NL, MU, YP, SL, SE.   Vic. Conservation status: native Flowering time: May — July.

SA Distribution Map based on current data relating to specimens held in the State Herbarium of South Australia

Biology: This species has been confused with Pterostylis alata. The two species favour different habitats but where they are sympatric intermediates do not occur. A very low percentage of plants actually flower. Putative hybrids have been reported with P. robusta (MU).

Taxonomic notes: Affinis Pterostylidi alatae(labill) H.G. Reichb., a qua flore parum robustiore rufo-brunneo-vittato, interdum viridi et albo; et labello elongato fere lineari per sinus multo exserto, differt. Holotype: South Australia, 20km E. of bow hill, in sand dunes under Callitris, (c. 34º53'S 139º37'E) 10 June 1981, R. Bates 959 (AD). Isotypes: AD, BRI, CBG

Author: Not yet available