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Key.
Petals hardly a third as long as the lateral sepals, labellum apiculate, obtuse or emarginate, dorsal sepal horizontal or recurved …….var. typicus
Petals as long or longer than the lateral sepals, labellum with an acuminate lobe, dorsal sepal incurved …………… var. longipetalus
a. Corybas macranthus var. typicus Hh. (Nematoceras macrantha Hook f., sens. strict.)
Up to 22 cm. high. Leaf solitary, petiolate, up to 4 cm. long by 4 cm. broad, ovate-cordate, mucronate, light green above, silvery below, often marked with purple. Floral bract acute, secondary bract similar, smaller. Flowers 1–2, sessile, purplish, green or red. Dorsal sepal acuminate, usually longer than the labellum, horizontal or recurved. Lateral sepals erect, filiform-caudate. Petals similar, about a third as long, often horizontal. Labellum with 2 rounded auricles at the base. Lamina expanded roughly funnel-shaped, the anterior margin irregularly crenulate, obtuse emarginate or apiculate. Column short, erect, or slightly incurved, the wings exceeding the anther. Seeding peduncle up to 20 cm.
Distribution. Endemic—abundant throughout New Zealand, tending to be less common in the north. Also in Stewart, Chatham, Auckland and Campbell Islands.
Flowers July to January, sea level to 5,000 feet. Large colonies on the forest floor or along the banks of rivers.
Hooker's illustration under Nematoceras macrantha (Fl. Nov. Zel., 1, 1853, 250, t. 57 a.) can be regarded as the hypotype of the species. Probably derived from an early form of C. trilobus. Occasionally the petals are furnished with irregular, fleshy lobes. Stewart Island has a beautiful pink-flowered form, morphologically identical with the normal, but which breeds true to colour-type.
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b. Corybas macranthus var. longipetalus Hh. var. nov.
Macranthus typicus affinis, subsimilis. Differto sepalum dorsale incurvum; petala longissima; lamina labellae lobata et acuminata.
Up to 6 cm. high. Similar to but rather smaller than the type, and differing in the very long petals, the lobed labellum and the incurved tip to the dorsal sepal. The lateral sepals are often horizontal. Flowers red or translucent. Seeding peduncle up to 15 cm.
Distribution. Endemic—5, abundant along the banks of streams throughout the tussock hill country lying between the Moawhango and Wangaehu Rivers to the south-east of Mt. Ruapehu. 1942–5 (E. D. Hatch); 16, specimens in seed, almost certainly belonging to this variety, have been found at Butterfields Beach, Stewart Island, 11, 1946 (C. Smith); 12a, Kelly Creek, Otira River, 1, 1947 (P. Haddon-Jones).
Holotype. In Herb. Hatch, No. 563, Waitangi Stream (Wai-ouru), 3,000 feet, September 2, 1944, E. D. Hatch.
Flowers September to November, 3,000 to 4,000 feet, descending to sea level in Stewart Island. Small colonies.
Probably derived from C. macranthus typicus. The accompanying illustration can be regarded as the hypotype of the variety.
7. Corybas rivularis (A. Cunn.) Reichb. f., l.c. Hatch Trans. R.S.N.Z., 75, 1945, 368.
Up to 15 cm. high. Leaf solitary, sessile, up to 4 cm. long by 25 mm. broad, ovate-acuminate, repand, light green above, silvery beneath, with conspicuous reddish veining. Floral bract shortly caudate, secondary bract subulate. Flowers solitary, sessile, more or less translucent, with dull red striae. Dorsal sepal extended into a filiform cauda. Lateral sepals erect and very long, exceeding the flower by as much as 6 cm. Petals similar, smaller, horizontal or deflexed. Labellum with 2 rounded auricles at the base. Lamina expanded, abruptly recurved against the ovary, mucronate, irregularly fimbriate, or entire. Column short, basal callus large. Stigma orbicular, column-wings minutely denticulate and exceeding the anther. Seeding peduncle up to 18 cm
Distribution. Endemic—occasional throughout New Zealand, Stewart and the Auckland Islands. tending to be rather local.
Flowers September to November, sea level to 2,000 feet. Large colonies on the forest floor.
Probably derived from an early form of C. trilobus.