Pterostylis russellii



Pterostylis russellii, commonly known as Russell's greenhood, is a species of orchid endemic to eastern Australia. Non-flowering plants have a rosette of leaves flat on the ground but flowering plants have a single shiny white and dark green flower on a flowering stem lacking a rosette but with a few spreading stem leaves.

Description
Pterostylis russellii is a terrestrial, perennial, deciduous, herb with an underground tuber and when not flowering, a rosette of between three and six dark green, oblong to heart-shaped leaves, each leaf 15-40 mm long and 10-18 mm wide. Flowering plants have a single shiny dark green and white flower 15-20 mm long and 7-9 mm wide on a stem 200-350 mm tall with three to five stem leaves. The dorsal sepal and petals are fused, forming a hood or "galea" over the column curving forward in a semi-circle. The dorsal sepal ends with a thread-like tip 3-7 mm long. The lateral sepals are held closely against the galea, have erect thread-like tips 20-30 mm long and a protruding, V-shaped sinus between their bases. The labellum is about 11-14 mm long and about 3 mm wide, blackish, blunt and protruding above the sinus. Flowering occurs from April to August.

Taxonomy and naming
Pterostylis russellii was first formally described in 1952 by Trevor Hunt from a specimen collected near Brisbane and the description was published in The Orchid Journal (California). The specific epithet (russellii) honours "Mr. A.J. Russell, then Captain Russell, a keen and competent student of Australian orchids" who first collected this species.

Distribution and habitat
Russell's greenhood grows in moist, shady places in forest between Grafton in New South Wales and Gympie in Queensland.