TAXONOMIC REVISION OF GEESINKORCHIS ( COELOGYNINAE ; EPIDENDROIDEAE ; ORCHIDACEAE )

The orchid genus Geesinkorchis de Vogel (Coelogyninae; Epidendroideae) was first described in 1984 by De Vogel to commemorate the late botanist Rob Geesink. According to De Vogel (1984), the characters distinguishing Geesinkorchis from other genera in the Coelogyninae are the successively flowering inflorescences in combination with small flowers, floral bracts caducous at anthesis, few sterile bracts, and the presence of a minute, thin stipe. The latter structure was recently identified as a caudicle rather than a stipe (Hsu et al., unpubl. data). Although caudicles are common in other Coelogyninae, phylogenetic studies of the subtribe so far (Gravendeel, 2000; Gravendeel et al., 2001; Gravendeel et al., 2005) indicate that Geesinkorchis can be considered a separate genus, nonetheless. In all publications on Geesinkorchis to date, only two species from Borneo are mentioned (De Vogel, 1986; Beaman et al., 2001; Wood, 2003). In the past decade, plant material was collected in Indonesia and Malaysia that did not match the existing descriptions (Beaman et al., 2001) and two new species of Geesinkorchis are published here together with an updated generic description.


INTRODUCTION
The orchid genus Geesinkorchis de Vogel (Coelogyninae; Epidendroideae) was first described in 1984 by De Vogel to commemorate the late botanist Rob Geesink.According to De Vogel (1984), the characters distinguishing Geesinkorchis from other genera in the Coelogyninae are the successively flowering inflorescences in combination with small flowers, floral bracts caducous at anthesis, few sterile bracts, and the presence of a minute, thin stipe.The latter structure was recently identified as a caudicle rather than a stipe (Hsu et al., unpubl. data).Although caudicles are common in other Coelogyninae, phylogenetic studies of the subtribe so far (Gravendeel, 2000;Gravendeel et al., 2001;Gravendeel et al., 2005) indicate that Geesinkorchis can be considered a separate genus, nonetheless.
In all publications on Geesinkorchis to date, only two species from Borneo are mentioned (De Vogel, 1986;Beaman et al., 2001;Wood, 2003).In the past decade, plant material was collected in Indonesia and Malaysia that did not match the existing descriptions (Beaman et al., 2001) and two new species of Geesinkorchis are published here together with an updated generic description.
Epiphytes (sometimes also terrestrial or lithophytic Habitat & Ecology -Epiphytes, sometimes growing on the ground or on rocks, in montane forest or kerangas vegetations on podsolic soils in the shade to full sun, between 400-2000 m above sea level.
Conservation status -Geesinkorchis quadricarinata and G. breviunguiculata are known from few collections only and must be considered rare.Geesinkorchis alaticallosa and G. phaiostele are locally common in Brunei, Sarawak, Sabah, and Kalimantan, but suitable habitats are rapidly decreasing.
Artificial hybrids -None registered.
2. Pedicel and ovary apple green; sepals and petals light yellow; lip white or light yellow, tinged reddish brown; callus white, tinged reddish brown; column chocolate brown to dark maroon; anther rusty brown.Sweet smell.
3. This species can easily be recognized by the central erect ridge of the callus of the hypochilium.Geesinkorchis phaiostele (Ridl.)de Vogel (1984) 198;(1986)   Notes -1.The epithet phaiostele (which is Latin for dark column) refers to the maroon column.
2. Pedicel and ovary pink; sepals and petals light yellow; lip white, with small central brownish tinged patch; callus white; column light brown to very dark maroon; anther orange brown.Sweet smell.
2. Pedicel and ovary green; sepals and petals brownish ochre; lip yellowish cream, with two brown lines bordering the front of the raised median band with the keels; column hood dark brown, stigma ochreous.Smell not recorded.
3. This species can easily be recognized by the four keels of the callus; two on the hypochilium and two on the claw, and the broadly triangular-ovate apex of the epichilium.Callus consisting of two lateral keels but without an elevated central ridge, starting beyond the hypochilium base and ending at the basal portion of the epichilium, 2.6-3 by 1.5-1.9mm, keels running along the whole length of the callus, in front gradually lowering, 0.7-0.9mm high at the base, 3-4 mm high in front, apex glabrous.Epichilium suborbicular when flattened, 3. Notes -1.The epithet breviunguiculata (which is Latin for shortly clawed) refers to the short claw of the lip.
2. Pedicel and ovary green; sepals and petals ochre yellow; lip light yellow, faintly orange-brown at the base; margins of the midlobe white; keels white at the base of the lip, in front with light brown edge.Smell not recorded.
3. This species can easily be recognized by the suborbicular and indistinctly clawed epichilium.
). Roots sparsely branched, puberulous.Rhizome creeping, sometimes branched.Pseudobulbs close together, elliptic or narrowly ovoid, flattened, with two to several longitudinal ridges.Scales of the young shoot triangular, imbricate, distichous, papyraceous to thin pergamentaceous, soon dry but long persistent, finally disintegrating into fine fibres, nerves many, apex acute.Leaves two per pseudobulb, petiolate; petioles deeply channelled; blade narrowly (ob)ovate, subcoriaceous to coriaceous, more or less stiff, main nerves prominent, other nerves much less so to rather indistinct, apex acute.Inflorescence terminal, erect, rigid, starting proteranthous, continuing to produce flowers in succession until long after the pseudobulb and leaves are fully developed.Peduncle erect, consisting of one internode, not elongating after anthesis, long, sturdy.Rachis elongating during anthesis, straight to zigzag; internodes short.Sterile bracts at base of the rachis absent or few, caducous at anthesis.Floral bracts entirely covering the young floral buds, closely imbricate, distichous, pergamentaceous to papyraceous, caducous at anthesis, triangular, with several groups of minute, stellately arranged uniseriate hairs inside, folded along the midrib; nerves many, fine, apex acute.Flowers up to 150, opening in succession from the base upwards, one or two open at the same time, widely opening; lip mostly turned downward.Pedicel curved, terete to more or less angular.Ovary more or less angular with 3 rather prominent ribs.Median sepal deeply concave, ovate, hairy inside just like the floral bracts; midrib prominent; apex acute.Lateral sepals oblique, ovate to ovate-elliptic, hairy inside just like the floral bracts, concave in the basal half, midrib usually prominent and keel-like, apex acute.Petals linear, sometimes oblique, curved or slightly rolled backwards, nerves 3, apex rounded to truncate.Lip pandurate when flattened.Hypochilium base saccate, hairy or glabrous, with or without keels, lateral lobes triangular or spatulate, often oblique, apex curved upward or erect or Pollinia 0.6-0.8 by 0.35-0.5 mm.Caudicle 1.3-1.8 by 0.3-0.4mm, with two oblong lateral lobes connected to the base of the pollinia, 0.25-0.35by c. 0.1 mm.Stigma including rostellum ovate in outline, 2.3-2.7 by 1.5-1.8mm; rostellum triangular, apex acute.Capsule 16-20 by 8-11 mm.Seeds 0.5-1 by 0.2-0.3mm.Distribution -Borneo: Brunei, Kalimantan, Sabah, Sarawak.