Corybas limpidus

Corybas limpidus is a terrestrial, perennial, deciduous, herb with a single thin, round or broad heart-shaped leaf 20–35 mm (0.8–1 in) long and wide. The leaf is green on the upper surface and silvery green on the lower side. There is a single erect, translucent green flower with dark red spots and blotches, 10–15 mm (0.4–0.6 in) long and 7–10 mm (0.3–0.4 in) wide. The dorsal sepal is burgundy-coloured, 16–18 mm (0.6–0.7 in) long and 5–7 mm (0.2–0.3 in) wide and curves forward over the labellum. The lateral sepals are green, about 5 mm (0.2 in) long, 0.5 mm (0.02 in) wide, joined at their bases and taper to a fine tip. The petals are about 3 mm (0.1 in) long, 0.5 mm (0.02 in) wide and taper to a thread-like tip. The labellum is longer than the dorsal sepal, 8–11 mm (0.3–0.4 in) long, 7–9 mm (0.3–0.4 in) wide with a greenish mound in the centre. The edges of the labellum have a few short, blunt teeth. Flowering occurs in August and September.[2][3][4][5][6]

Corybas limpidus was first formally described in 1991 by David Jones, in Australian Orchid Research, based on specimens collected near Albany in 1986.[2][7] The specific epithet (limpidus) is a Latin word meaning "clear", "transparent" or "pure",[8] referring to the dorsal sepal and part of the labellum.[3]

In 2002, David Jones and Mark Clements proposed splitting Corybas into smaller genera and placing this species into Corysanthes but the change has not been widely accepted.[9]

The crystal helmet orchid grows under dense shrubs between sand dunes in coastal areas from Esperance to Walpole in the Esperance Plains, Jarrah Forest and Warren biogeographic regions.[4][5][6][10]

Corybas limpidus is classified as "Priority Four" by the Government of Western Australia Department of Parks and Wildlife,[10] meaning that is rare or near threatened.[11]