Tridactyle nanne-ritzkae Eb.Fisch., Killmann, J.-P.Lebel & Delep., Orchidee (Hamburg) 64: 350 (2013).
Description:
Epiphytic orchid, stem erect, 12-50 (95) cm long. Leaves distichous, spreading, linear, 8-10 cm long and 1.5 cm wide, unequally bilobed at apex. Inflorescence up to 5 cm long, with up to 10 flowers. Bracts distichous, 0.27 x 0.14 cm. Flowers greenish, dorsal sepal 0.35-0.6 x 0.2 cm, obtuse at apex, lateral sepals 0.39-0.4 x 0.25-0.3 cm, elliptic, petals oblong to elliptic, acute, 0.32 x 0.1-0.13 cm, lip 3-lobed, 0.430.45 x 0.24 cm, basal auricles slightly bilobed, 0.1 x 0.8 cm, mid-lobe broadly triangular and acute, 0.085-0.095 cm long, 0.09-0.1 cm wide at base, side lobes as long as or slightly longer than mid-lobe, not reaching the apex of the mid-lobe, 0.1-0.15 cm long and 0.02-0.03 cm wide at base, narrowly filiform with entire or rarely slightly bifid apex, spur slightly curved downwards, inflated at apex, (0.38) 0.46-0.6 (0.67) cm long and 0.09-0.12 cm wide, obtuse at apex, column 0.150.17 cm long, ovary and pedicel 0.43-0.45 cm long.
Etymology:
This species is dedicated to Mrs Marianne Ritzka on the occasion of her 100. anniversary by her son Hans Klieber.
Habitat:
Epiphyte in montane rainforest and Ericaceous shrub, 2450-2900 m, growing on Erica johnstonii and Agarista (=Agauria) salicifolia.
Flowering season:
February to March, November to December.
Notes:
Tridactyle nanne-ritzkae is closely related to Tridactyle bicaudata and Tridactyle Tridactylites. It differs from both taxa in the erect habit (usually pendulous in Tridactyle tridactylites and Tridactyle bicaudata). It can be distinguished from the first by the greenish flowers (yellow green in Tridactyle tridactylites), the shorter and broader triangular mid-lobe of lip, the side lobes of the lip shorter or equalling the mid lobe (longer than mid lobe in Tridactyle tridactylites) and the much shorter spur which is inflated at apex (narrow filiform and not inflated in Tridactyle tridactylites). It differs from Tridactyle. bicaudata in the greenish flower colour (white, greenish to orange yellow in Tridactyle bicaudata), the broader and shorter midlobe of lip, the shorter and entire side lobes of the lip (longer than mid-lobe and laciniate at apex in Tridactyle bicaudata), and the shorter, slightly curved and apically dilated spur (straight, filiform much longer and only slightly dilated at distal middle in Tridactyle bicaudata).
Distribution:
Rwanda, only known from the type locality in Nyungwe National Park near summit of Mt. Bigugu and from a second locality near Uwinka.
References:
World Checklist of Monocotyledons. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the Internet; http://www.kew.org/wcsp/monocots/ accessed 21.03.2017
Images:
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