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| FIGURE 3. Exacum zygomorpha Aver. & K.S.Nguyen, sp. nov. A: Flowering plants in native habitat. B: Flower bud at the beginning of anthesis. C–E: open flowers, views from different sides.
All photos from the type — CPC 6183 by Khang Sinh Nguyen, correction and design by L.Averyanov. DOI: 10.11646/phytotaxa.183.2.3
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Abstract
The paper provides a key for identification and a checklist of mycoheterotrophic species of the genus Exacum, representing a well-defined group of achlorophyllous members of Gentianaceae regarded sometimes in the limits of a separate genus Cotylanthera. One novel species, Exacum zygomorpha, discovered in northern Vietnam, is described and illustrated as new for science. Among other features the discovered species strikingly differs from its congeners in having distinctly zygomorphic flowers.
Keywords: Cotylanthera, Cotylanthera zygomorpha, Exacum, Gentianaceae, Indochina, Vietnam, Laos, plant diversity, plant taxonomy
Exacum zygomorpha Aver. & K.S.Nguyen, sp. nov
Etymology:— Species name refers to distinct zygomorph–like asymmetry of its flowers.
Distribution:— Vietnam (Nghe An). Only one locality in Phu Xai Lai Leng Mountain on the border of the
provinces Xiangkhouang (Laos) and Nghe An (Vietnam).
Ecology:— Primary humid shady broad-leaved and mixed forests (with Cunninghamia konishii) on soils rich
in humus derived from sandstone and shaly rocks at elev. 2000–2300 m, usually along ridge edges. It flowers from
October–November. Very rare.
Leonid V. Averyanov, Khang Sinh Nguyen and Hiep Tien Nguyen. 2014. Checklist of Mycoheterotrophic Species of the Genus Exacum (Gentianaceae) and New Species, E. zygomorpha, from northern Vietnam. Phytotaxa. 183 (2): 108–113. DOI: 10.11646/phytotaxa.183.2.3