A review of the Thai species of the Calanthe group (Orchidaceae) is presented, based on the examination of over 500 herbarium and spirit specimens, and is a precursor for a later treatment in the Flora of Thailand. The group comprises the genera Calanthe R.Br., Phaius Lour. and Cephalantheropsis Guillaumin. In the genus Calanthe, 21 species are recognized, one of them being new but incompletely known as only a single flower was available for study. Calanthe angustifolia (Blume) Lindl. is newly reported for Thailand. Unusual forms of C. vestita Wall. ex Lindl. are commented on, and the extensive variation in the spur length of C. triplicata (Willemet) Ames is discussed. Five Phaius and one Cephalantheropsis species are recognized. Identification keys to the three genera and all species are given, and descriptions are provided for all species. A selection is illustrated by line drawings.
Orchidaceae, Calanthe, Phaius, Cephalantheropsis, Thailand