Oberonia aureolabris Geiger, 2017

Geiger, Daniel L., 2017, Studies on Oberonia 2 (Orchidaceae: Malaxideae): Oberonia aureolabris, a new species discovered in cultivation, Phytotaxa 329 (2), pp. 173-179 : 174-178

Oberonia aureolabris Geiger , sp. nov. ( Figs. 1–3 )

Type :— INDONESIA. Java: western portion, 1500 m ; 7.0±0.7˚S, 108.25±2.25˚E, unknown collector, 2 August 2017, (holotype: HNT 12607 ). The holotype consists of a pressed plant with images of flowers on two sheets, ethanol preserved flowers and critical point dried, gold-coated flowers mounted on one SEM stub. SEM mounts are not typical preparations of types in botany. They are permissible under ICN Arts 8.2 and 8.3, and are referred to in Art. 9.8 Ex. 4. The material is considered important because it has some of the figured specimens .

This new species is similar to Oberonia rufilabris Lindley (1838 : t. 8 A), but with an orange flower, lip with panduriform inflated disc, one pair of long lateral lobes in middle of lip, epichile unequally trifid, large outer lobes 25–30% as long as lip and a minute lobe in midline.

Epiphytic herbs, up to 10 cm tall. Roots fibrous, c. 1 mm in diameter, off white. Leaves light green, irregularly falcate bending away from axis, base narrower than middle, acuminate to acute tip, basal leaves largest, proportionally wider than more apical leaves, basal leaf length 8 cm, width at base 0.8 cm, maximum width 1.2 cm about 3 cm from base; apical leaf length 4.7 cm, width at base 0.5 cm, maximum width 0.6 cm c. 2.5 cm from base. Leaves imbricate, resulting in densely leafed stem. Inflorescence terminal, 10.5 cm long; peduncle approximately 12 mm, infertile bracts sparsely scattered, long (~ 3 mm), aristate; rachis in cross section obtuse-angulate, glabrous; flowers in ill-defined whorls to scattered, approximately 8–10 per “whorl”, first flowers opening in apical third of inflorescence. Flower non-resupinate, orange. Floral bracts broad, clasping at base, acuminate, about ¼ longer than flower, glabrous, with approximately four to six thickenings. Sepals ovate acute. Lateral petals narrow lanceolate, shorter than sepals. Lip overall rectangular, base with panduriform inflated disc; lateral lobes linear, approximately at middle of lip, between lateral lobes and base sometimes irregular, shallow, inequilateral serrations; epichile trilobed; outer lobes acuminate, acute, 25–30% of length of lip, not spreading but more or less parallel to axis of flower; central lobule separating outer lobes; cells pneumate with glabrous surface. Gynostemium vasiform, clinandrium forming expansive shelf; anther cap light orange, covering half of clinandrium, cell surface sculpture finely rugulate, pneumate; pollinaria light orange-dark yellow. Pedicellate ovary with weak longitudinal, blunt ridges, glabrous.

Etymology:— aureo, Latin for golden/orange; - labris, Latin for lip. Referring to the golden coloured lip and similarity to O. rufilabris .

Notes:— The holotype is a cultivated specimen obtained from Popow Orchids, who indicated (pers. comm. 7/2017) that the stock plant originated from western Java. The elevation indication agrees with the plant being better cultivated in intermediate (15–28˚C) conditions as opposed to warm (21–35˚C). A new Oberonia species from western Java is not unlikely. In Comber’s (1990) volume on the orchids of Java, it was noted that he had found several Oberonia plants that did not fit any of the known species.

The distinguishing features include a unique panduriform inflated disc, short lobes of the epichile (less than a third of the length of the lip) that are also more widely separated from each other and the more or less equal length of the floral bracts over the entire flower-bearing portion of the inflorescence, longer at base of inflorescence than at tip in O. lotsyana Smith (1905: 241) and O. rufilabris ( Table 1, Fig. 4 ).

Although Oberonia species are known for their “annoying variability” ( Santapau & Kapadia 1966), and many unrecognised synonyms need to be addressed (Geiger, unpubl. data), O. aureolabris is clearly different from any other known Oberonia species. The inflated disc at the base of the lip is a distinct character and diametrically opposite to the much more common single or double sac on a more or less flat disc. It is known only in two other species, O. rufilabris and O. lotsyana . The panduriform shape of the inflated disc distinguishes O. aureolabris from the other two. Some other species have raised modifications of the usually flat surface of the disc, e.g., O. ensiformis (Smith 1812: 182) Lindley (1859: 4) with paired warts, O. setigera Ames (1912: 10) with annular ring, but the strongly inflated disc is restricted to the species mentioned.

The orange colour of the flower is equally distinct among the species with the inflated disc at the base of the lip. Although many Oberonia species vary widely in flower colour, the fairly common O. rufilabris has only red flowers. The same applies to the somewhat less well-known O. lotsyana . Based on the stable colour in O. rufilabris and O. lotsyana , it is expected that the flower colour is also constant in O. aureolabris , although it is not certain given the limited material available.

Floral bracts are an important character in Oberonia , in terms of both shape as well as relative length in comparison to the flower. They may be shorter than the pedicellate ovary but may be several times as long as the flower itself ( O. setigera ). In most species, the floral bracts are of the same length along the entire inflorescence, as is the case in O. aureolabris . Whereas the condition found in O. aureolabris is the norm for Oberonia , it is at variance to the other species with an inflated disc at the base of the lip, which readily distinguishes the new species.

It is unlikely that O. aureolabris is a rare mutant plant. Although a number of aberrations and (pseudo-)peloric flowers are known (Geiger & Kocyan in press), those modifications are usually only found on a few flowers of an inflorescence with otherwise typical flowers.Accordingly, the panduriform inflated disc and the orange colour seem to be a species-specific characters and not simultaneous aberrations. In fact, O. aureolabris is more distinct than O. rufilabris is from O. lotsyana . Given the known intermediates between the last two with respect to the degree of serration between the lateral lobe and the base, one may consider the two as synonyms. I retain them for the time being.

From species with abundant material in cultivation, O. rufilabris in particular, flowering plants may differ in size by a factor of five; small flowering plants tend to have small inflorescences with no more than three whorls of flowers, whereas large plants may have approximately 60 whorls of flowers. The arrangement and density of the flowers on the rachis is highly variable and a poor taxonomic character. Inflorescences of O. setigera that change from spiral arrangement to whorls on the same inflorescence are a case in point (Geiger unpubl.). Oberonia leytensis Ames (1920: 291) specimens with closely spaced flowers (flowers almost touching) to widely spaced flowers (whorls separated by about as much as the height of the flower) are known (Geiger unpubl.).

Oberonia has a number of proposed taxonomic sections. The application of those sectional names is not straightforward at all. In fact, less than half of the species names have ever been assigned to a section. The species with inflated disc may best fit in the section Arachnochilus , given the thread-like lateral lobes of the lip. I consider the following species to belong in the section Arachnochilus : elbertii Smith (1925: 5) , griffithiana Lindley (1838 : t. 8B), insectifera Hooker (1890 : pl. 21, t. 2004), jenkinsiana Griffith ex Lindley (1859: 4) , lotsyana , punamensis Schlechter in Schumann & Lauterbach (1905: 115), rufilabris , stenophylla Ridley (1896: 218) and probably also setigera . This list excludes various synonyms currently still considered correct by Govaerts et al. (2017). Whether a distinct section could even be justified for the species with inflated disc is open to further investigations.

The holotype flowered in July/August in cultivation. It is unclear whether this is a good indication for potentially finding flowering plants in nature. Although some species seem to show remarkably consistent phenological patterns even in cultivation (e.g., O. leytensis : Geiger pers. obs.), others seem to adapt to cultivation by flowering throughout the year. The latter is the case in O. rufilabris , which has been recorded to flower from October through April in nature ( Ansari & Balakrishnan 1990, Averyanov 2013, Backer & Bakhuizen van der Brink 1968: as O. valetoniana, Banerji 1982 , Banerji & Thapa 1971, 1978, Chowdhery 1998, Chowdhery & Pal 1997, Ding & Yin 2005, Gogoi & Yonzone 2016, Haines 1924, Lucksom 2007, Pradhan 1979, Raskoti 2009: also as O. nepalensis, Seidenfaden & Smitinand 1959 , Shakya & Chaudhary 1999: also as O. nepalensis and O. pantlingiana, Singh 2015 , Stainton 1988, Xinqi et al. 2009), but flowers throughout the year under cultivation (Geiger pers. obs.).

Figures

FIGURE 1. Oberonia aureolabris. A. Habit (scale bar = 10 cm). B. Portion of inflorescence (scale bar = 10 mm). C. Enlarged portion of B (scale bar = 1 mm). D. Lateral view of flower showing inflated sac (scale bar = 1 mm). E. Frontal view of flower showing lateral lobes and fine serrations towards base (scale bar = 1 mm). B–C: z-stacked on stereomicroscope. D–E: z-stacked on compound microscope. (Photographs of the material that became the type.)

FIGURE 2. Oberonia aureolabris, SEM images of flowers from the holotype.A–C. Frontal. D–E. Oblique. F. Medial without floral bract. G–H. Medial with floral bracts (scale bar = 1 mm). Arrows point to an irregular serration between main lateral lobe and base of lip.

FIGURE 3. Oberonia aureolabris, SEM details of flowers from the holotype.A–C. Inflated disc frontal (arrows highlight constriction in the panduriform disc. *: sac). D. Oblique view of inflated disc. E. Cell on middle of lip with glabrous pneumate surface sculpture (scale bars = 100 μm).

FIGURE 4. Oberonia species similar to O. aureolabris. A. SEM of flower of Oberonia lotsyana (K 52868, Comber 1724). B–F. Oberonia rufilabris. B. HNT 13047, ex cult. C. L17649. unknown/s.n. Slope of Gurung Penrissen, Borneo, Indonesia. D. L18987. Hortus Singapore 2790. E. L19257. Hortus Singapore/s.n. Ubi. F. Private collection. Z-stack of 67 images on compound microscope. Note orange pollinaria (scale bar = 1 mm).