Oberonia rhizomatosa J.J.Sm.

Geiger, D. L., 2020, Studies in Oberonia 8 (Orchidaceae: Malaxideae). Additional 24 new synonyms, a corrected spelling, and other nomenclatural matters, Blumea 65 (3), pp. 188-203 : 199-201

Oberonia rhizomatosa J.J.Sm. — Fig. 13 , 14

Oberonia rhizomatosa J.J.Sm. (early 1911a) 2; (1911b) 531,pl. 79A. — Syntype: Gjellerup 156 (BO), German New Guinea, Bougainville Mountains.

Oberonia repens Schltr. (11 Oct. 1911 a) 161; (1923) pl. 62, f. 221. — Syntype: Schlechter 20045 (B, lost), [ Papua New Guinea,] in the forests of the Torricelli mountains, 600 m, syn. nov.

Oberonia torana J.J.Sm. (1915) 216, pl. 70, f. 122. — Syntypes: Gjellerup 777 (BO), Indonesia, Irian Jaya, Berkombor at Tor river , 25 m; Gjellerup 912 (BO, L 0061802), Indonesia, Irian Jaya, Gauthier mountains on N slope, 300 m, syn. nov.

Oberonia ponapensis Tuyama (1940) 275, pl. 2, f. i. — Type: Hatusima 11102 (holo TI 12969 ; iso TI 12968 ), Caroline Islands [Federate States of Micronesia],Ponape [= Pohnpei],at peak of Mount Troton , 600 m, syn.nov.

Hippeophyllum microphyllum S.C. Chen (2003) 180, f. 1 (non Oberonia microphylla (Blume) Lindl. ). — Oberonia chenii Ormerod (2004) 378. — Type: van Royen & Sleumer 7662 (holo K 000942975; iso L.1512780), Indonesia, Irian Jaya, Vogelkop Peninsula, Ilje River valley, path from Banfot to Sudjak, 840 m, syn. nov.

Notes — Oberonia rhizomatosa and O. repens were both described in 1911. Schlechter’s O. repens is precisely dated to October 11, 1911. The description of O. rhizomatosa was on page 2 of the volume published in 1911, so most likely in the first half of the year. Accordingly, Smith’s name is taken as the correct name for this species. The fact that Schlechter referred to O. rhizomatosa in his description of O. repens further supports the earlier publication date for O. rhizomatosa .

The illustrations in Smith (1911b) were given with fractional size indications, which were used as basis to scale the floral elements to same relative size. The 1 mm scale bar is derived from the absolute size indications in the Latin protologue, where the longer scale bar is based on the lip, while the shorter is based on the measurement for the sepal. The difference between the two scale bars is over 40 %. It is a further example of how imprecise measurements and scales are in descriptions of Oberonia . Accordingly, such measurements should be viewed with much caution, and minor size differences in the literature are most likely due to measurement errors.

Additionally, the shape of the lip differs between the drawing of the entire flower and in the illustration of the parts. For the entire flower, the lateral lobes are more narrow than the epichile lobes, while those relations are reversed in the isolated lip. The lateral lobes are shown without auricles in the entire flower, but with distinct auricles in the isolated lip.

Oberonia repens is a synonym of O. rhizomatosa . The shared characters include the uncommon creeping habit, narrow leaves and the overall shape of the lip. Schlechter (1911a: translated from original German) noted the similarity to O. rhizomatosa and indicated that ‘the labellum and petals in the here described species seem to be quite different’ without elaborating on any specifics.

The description of O. torana was based solely on Gjellerup 777, so should be given preferential standing; however, the repository of that gathering is uncertain as the specimen was not figured by Schuiteman & De Vogel (2006). Smith (1915) wondered whether O. torana might be the same as O. repens , but did not compare his O. torana to his earlier O. rhizomatosa . The descriptions and flower drawings leave no doubt about Smith’s conclusion. The creeping rhizome, the moderately caulescent habit with long, thin, falcate leaves also seen in Gjellerup 912 specimens, are in prefect agreement with O. rhizomatosa .

Oberonia ponapensis shares the rather uncommon creeping habit, moderately caulescent growth with narrow leaves, and the flower with lobed petals and the lip with upward-turned, trapezoidal lateral lobes and two lobes of the epichile. The habit of the two growths mounted on the holotype sheet ( Fig. 13h ) show how smaller plants are little caulescent similar to Smith’s drawing of O. rhizomatosa , while larger plants develop a more caulescent habit. Notice the horizontal rhizome at the base of the larger two growths.

The epichile lobes were described by Tuyama (1940: 275) as ‘falcatos triangulos acutos producta’, which is different from the rounded lobes seen in the SEM images shown here. While Tuyama did not illustrate the flower, a specimen from Ponape identified as O. ponapensis and with identical habit could be examined ( Fig. 13i ). The imperfectly rehydrated flower shows lateral lobes wider than the epichile lobes, and the epichile lobes appear to be more curved with pointed tip similar to Tuyama’s description. Those differences, though, can easily be attributed to artefacts due to drying and rehydration of the flower, including the necessary unfolding of overlapping floral elements. The right petals with erose margin appears to have a rather narrow shape. The latter is due to the top margin being folded over, and is remarkably similar to J.J. Smith’s (1911b, see Fig. 13a ) illustration of O. rhizomatosa . The white rectangular inclusions are calcium oxalate raphide bundles (Geiger unpubl. data).

Oberonia ponapensis was compared to O. brunnea Schltr. , O. linearis Schltr. , O. radicans Schltr. with similar lateral lobes but much more pointed lobes of the epichile, and most importantly without creeping rhizomes.

Hippeophyllum micranthum = O. chenii is another synonym of O. rhizomatosa . It shares the uncommon creeping habit, the serrated lateral petals and the quadrilobed lip with O. rhizomatosa . The flowers were described as dark red in colour, as in O. repens by Schlechter (1911a), and 0.8 mm wide. Chen (2003) did not compare his species to any others, and did not include a single reference in his description. A perusal of Schlechter’s (1911a) well-known work from the same region would have quickly identified his plant to at least one of the already described names.

Figures

Fig. 13 a–c. Oberonia rhizomatosa drawings from Smith (1911b). a. Habit; b. entire flower; c. floral parts including bract; 1 mm scale bars based on contra- dictory scale and size information in Smith (1911a, b); d. Oberonia torana drawing from Smith (1915), including two separated lips and the floral bract; e–f. Hippeophyllum microphyllum from Chen (2003); e. habit;f. flower and bract; g. drawing of O. repens from Schlechter (1923:pl. 62,f. 221); h. habit of two plants from holotype Hatusima 11102 TI 12969 of O. ponapensis; i. rehydrated flower from Ponape Glassman 2857 F 2272001. — Scale bars c, f = 1 mm; e = 2 cm.

Fig. 14 Oberonia rhizomatosa, whole flowers and seeds by SEM. a–c, e. Frontal, top with bract (Polak 699 L15582 from Irian Jaya); d. oblique view (Schuiteman 90/475 L22510 from Papua New Guinea); f. seeds (Darbyshire & Hoogland 8118 CANB 104114 from Papua New Guinea). — Scale bars: a–e = 1 mm; f = 100 µm.