AFRICAN

ORCHIDS

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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Tridactyle minutifolia Stévart & Haijere, Phytotaxa 212: 143 (2015).
Description:
Epiphytic herb with unbranched erect stem, 20–40 cm long and 2 mm in diameter, internodes 2–4 mm long, brownish to black spots. Roots up to 0.5 mm in diameter, glabrous. Leaves distichous; blade linear, 5–7 × 0.2–0.4 cm, glabrous, dull, green; apex unequally bilobate. Inflorescences up to 8 per shoot, opposite to the leaf, semi-pendulous, 3.5–5.5 cm long, 7–10 flowered. Floral bracts broadly triangular, apex acute, 1.5–2 × 1–1.5 mm. Flowers arranged in two rows, 2–4 mm spaced out, white-yellowish to orange. Pedicel and ovary 3–4 × 1 mm, papillose. Sepals ovate, acute to acuminate, 3–5 × 1–2 mm, adaxially 3-veined, the tips recurved, margins entire, glabrous. Petals linear, acute, 3–5 × 1 mm, margins entire or slightly dentate, glabrous. Labellum auriculate at the base, auricules ronded, 0.5–1 mm diameter; labellum trilobate to about half way, 5 × 1.3 mm, glabrous; mid-lobe 2.5–4 mm long, triangular; side lobes longer, spreading, almost threadlike. Spur mostly absent, or if present, 7–8 mm long, cylindrical, straight, apex acute. Flower scent not observed.
Habitat:
Epiphytic herb found in high canopy and dense rainforest with many Burseraceae, sometimes exploited. It was found as an epiphyte on Bikinia letestui (Pellegrin 1942: 120) Wieringa in Wieringa & van der Maesen (1999: 222) between 25 and 40 m in the canopy. The altitude range of the species was estimated to be between 350 and 490 m (for specimens with spur) and around 570 m (for specimens without spur).
Phenology:
Flowering in February, May and between October and December.
Cultivation:
As given for the genus.
Notes:
The length of the rachis and the shape of the side lobes of the labellum place the species in the section D of Tridactyle, according to Summerhayes (1948), which include species with long inflorescences (more than 4 cm) and entire side lobes of the labellum. It is also very close to Tridactyle stevartiana, a species occurring in Rwanda, based on the shape and length of the leaves but differs from it in the inflorescences and the margins of the side lobes. Indeed, Tridactyle stevartiana has inflorescences of 1 cm or less, while Tridactyle minutifolia has inflorescences of 3 to 6 cm, and the margins of the side lobes of Tridactyle stevartiana are denticulate while the one of Tridactyle minutifolia are entire. According to unpublished molecular data produced by the second author, using plastid matK, trnL-trnF and ITS, Tridactyle minutifolia is close to Tridactyle tridactylites, but it is well separated. In specimens Stévart 3054, Biteau 155 and GB 416 from Monts de Cristal and adjacent area, spur is lacking, but specimens from Monts Doudou (collected from the living plant Arends 634) have a long spur.
Distribution:
Endemic to Gabon and Equatorial Guinea. The distribution range of Tridactyle minutifolia is comprised in the Atlantic Sector of the Lower Guinea Domain (Senterre 2005), which is the coastal part of the Lower Guinea Domain of the Guineo-Congolian Region (White 1979).
References:
A new species of Tridactyle (Vandeae, Epidendroideae, Orchidaceae) from Gabon and Equatorial Guinea Phytotaxa 212 (2): 141–148.2015: 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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Tridactyle Group 3.
Description:
Inflorescences long, usually over 4 cm long and up to 20 cm long, bearing 6 or more flowers.
Species:

Tridactyle armeniaca (Lindl.) Schltr. W. Trop. Africa to Gabon, São Tomé.
Tridactyle aurantiopunctata P.J.Cribb & Stévart Príncipe.
Tridactyle bicaudata (Lindl.) Schltr. Trop. & S. Africa.
Tridactyle bicaudata subsp. bicaudata. Trop. & S. Africa.
Tridactyle bicaudata subsp. rupestris H.P.Linder S. Cape Prov. to KwaZulu-Natal.
Tridactyle brevicalcarata Summerh. Ghana to Gabon.
Tridactyle exellii P.J.Cribb & Stévart São Tomé, Gabon.
Tridactyle fimbriatipetala (De Wild.) Schltr. C. Zaïre.
Tridactyle gentilii (De Wild.) Schltr. Trop. & S. Africa.
Tridactyle latifolia Summerh. Príncipe, Gabon.
Tridactyle minutifolia Stévart & Haijere Gabon and Equatorial Guinea
Tridactyle nanne-ritzkae Eb.Fisch., Killmann, J.-P.Lebel & Delep. Rwanda
Tridactyle pentalobata P.J.Cribb & Stévart Gabon.
Tridactyle tridactylites (Rolfe) Schltr. Trop. Africa.
Tridactyle truncatiloba Summerh. Gabon.
Tridactyle unguiculata Mansf. SW. Tanzania.

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 31.10.2020










A key to the subspecies Tridactyle bicaudata

1a Plants epiphytic; leaves 60-120 mm long; flexuose subsp. bicaudata
1b Plants lithophytic; leaves 30-60 mm long; stiff and arcuate subsp. rupestris

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

Tridactyle Group 2.
Description:
Inflorescences short to medium sized, 1—4 cm long, bearing 3—8 flowers, sometimes more.
Species:

Tridactyle brevifolia Mansf. Tanzania (Nguru Mts., Uluguru Mts.).
Tridactyle cruciformis Summerh. Kenya to NE. Tanzania.
Tridactyle fusifera Mansf. W. Trop. Africa to Cameroon.
Tridactyle inaequilonga (De Wild.) Schltr. Tanzania to Zimbabwe.
Tridactyle lisowskii (Szlach.) Szlach. & Olszewski WC. Trop. Africa.
Tridactyle phaeocephala Summerh. E. Tanzania.
Tridactyle stipulata (De Wild.) Schltr. C. Zaïre.
Tridactyle thomensis P.J.Cribb & Stévart São Tomé.
Tridactyle trimikeorum Dare Zimbabwe.
Tridactyle verrucosa P.J.Cribb S. Tanzania to Malawi.
Tridactyle virginea P.J.Cribb & la Croix S. Tanzania to Malawi.

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