Mnesithea rottboellioides (R.Br.) de Koning & Sosef

Veldkamp, J. F., Heidweiller, J., Klaauw, M. A. F. van der, Koning, R. de, Kraaijeveld, A. R., Sosef, M. S. M. & Strucker, R. C. W., 2013, A revision of Mnesithea (Gramineae - Rottboelliinae) in Malesia and Thailand, Blumea 58 (3), pp. 277-292 : 286-287

9. Mnesithea rottboellioides (R.Br.) de Koning & Sosef — Fig. 10

Mnesithea rottboellioides (R.Br.) de Koning & Sosef in Veldkamp et al. (1986) 291. — Ischaemum rottboellioides R.Br. (1810) 205. — Andropogon rottboellioides (R.Br.) R.Br. ex Steud. (1854) 382. — Rottboellia ophiuroides Benth. (1878) 514, nom. superfl.; Hack. (1889) 303 (incl. var. genuina Hack. , nom. inval.). — Manisuris rottboellioides (R.Br.) Kuntze (1891) 779. — Rottboellia rottboellioides (R.Br.) Druce (1917) 644; Reeder (1948) 354,isonym. — Coelorachis rottboellioides (R.Br.) A. Camus (1921) 197. — Type: R. Brown 6156 (holo BM (photo BRI);CANB (?), MEL (photo BRI), NSW (photo BRI)).

Rottboellia ophiuroides Benth. var. commutata Hack. (1889) 304. — Coelorachis rottboellioides (R.Br.) A.Camus var. commutata (Hack.) Henrard (1941) 519. — Type: F. v. Mueller s.n. (holo W, fragm. & photo in BRI; photo K, MELB; iso BRI).

Rottboellia ophiuroides Benth.var. vestita Domin (1915) 261. — Type: Domin I 1910 (holo PR, photo BRI), Queensland, Yarraba , savannah forests.

Rottboellia ophiuroides Benth.var. intermedia Hack.(1906) 265. — Coelorachis rottboellioides (R.Br.) A.Camus var. intermedia (Hack.) Jansen (1953) 255. — Lectotype: Elmer 6393 (BO, K, PNH lost, W), designated here.

Coelorachis rottboellioides (R.Br.) A.Camus var. hirsuta Jansen (1953) 255. — Lectotype: Carr 11134 (holo L), here designated.

Plants perennial. Culms (0.6–)1.6–2.5(–3) m long, glabrous. Cataphylls ovate-oblong, (2–)18–26(–48) mm by (1.5–)6–9(–16) mm, glabrous, apex acuminate to mucronate. Nodes glabrous. Sheaths glabrous to hairy, margin glabrous to ciliate. Ligule 1.5–5 mm long, glabrous or margin ciliolate to setose. Contra-ligule glabrous to pubescent. Blades flat to folded, (13–)23–38(–95) cm by 2–27 mm, margins glabrous at base, hairy on both sides to glabrescent, glabrous to setose behind the ligule, smooth. Peduncles solitary or paired, glabrous. Spatheoles 2.5–7.5 cm long. Spikes 2–10.5 cm by 1–3 mm. Spikelets paired. Joints 2–3.4 mm long, glabrous, smooth. Sessile spikelets 2.5–4.2 mm long (incl. callus), longer than the joint. Callus glabrous. Lower glume flat, ovate-oblong, glabrous, chartaceous, smooth, greenish yellow to margins purplish, 6–8-nerved, lower part at keel smooth, apex winged; upper glume boat-shaped, ovate-oblong, 3–3.8 mm long, glabrous, 3–4-nerved, nerves not anastomosing, margin infolded, apex acute. Lemmas ovate-oblong, 2.4–3.2 mm long, glabrous, apex acute; first lemma epaleate, 2.7–3.2 mm long, 3-nerved; second lemma 2–3-nerved. Second palea ovate-oblong, 2.1–2.7 mm long, 2-nerved, glabrous. Anthers 1.2–2.1 mm long. Pedicel free from the joint, 1.8–3.8 mm long, glabrous, smooth. Pedicelled spikelets well-developed with a male or bisexual floret, dorso-ventrally flattened, 3–3.8 mm long. Lower glume chartaceous, glabrous, winged. Anthers 1.2–1.7 mm long. 2n =?

Distribution — Malesia: Philippines (Bohol, Cebu, Guimaras, Luzon, Mindanao, Panay, Siargao), Lesser Sunda Isl. ( Flores, Sawu, Tanimbar, Timor, Wetar), New Guinea: Irian Jaya: Jayapura, Merauke; Papua New Guinea: Central, Madang, Milne Bay, Morobe, Northern, Western Prov.; Australia (Queensland, Northern Territory, W Australia) and? Polynesia (fide Warburg 1890: 260), but not in e.g. Fosberg et al. (1987: 19).

Habitat — Sunny, grassy places, burned grasslands, savannahs, swampy areas, roadsides, along railroads, Eucalyptus forests, up to 2320 m altitude; locally dominant.

Vernacular name — Baron river tussock grass (E).

Uses — An analysis showed nutritional value to be consider- ably below the average ( Backer 1950: 176, as R. ophiuroides ). In Goodenough Island widely used for thatching ( Burcham 1948: 414, t. 2, 3).

Notes — The species is easily recognized by the smooth lower glume of the sessile spikelets apically with distinct auricles.

The var. commutata would be distinct by bulbous-based bristles on the lower glume of the sessile spikelets . This feature is variable within a single spike and therefore there seems to be no other reason to maintain this taxon.

A form described as var. vestita by Domin from Australia and as var. hirsuta by Jansen from New Guinea would be distinct by the presence of densely hairy sheaths (especially the upper ones) and blades (e.g. Carr 11134, lectotype of the second), but Hoogland 4690 and NGF 22056 (Gillison) have glabrous sheaths and hairy blades. Many specimens have blades that are pubescent on the upper surface only, and several have completely glabrous blades. It seems therefore impossible to maintain this variety.

In the Philippine var. intermedia the lower glume of the sessile spikelet is only shortly winged above the middle. The expres- sion of this feature, however, is quite variable, and insufficient to base a taxon on.

Van Borssum Waalkes 3156 (Tanimbar) and HÖft 3230 (Morobe Prov.) (L) have joints with two sessile and two pedicelled spikelets.

Differs from the Malesian / Thai congeners in: Cataphylls glabrous. Sessile spikelet callus glabrous; lower glume chartaceous. Pedicelled spikelets composed of 2 glumes and 1 male or bisexual floret.

Most similar is M. glandulosa :

1. Cataphylls puberulous to ciliate along the margin. Sessile spikelet callus ciliolate; lower glume coriaceous, laterally with small appendages................ M. glandulosa 1. Cataphylls glabrous. Sessile spikelet callus glabrous; lower glume chartaceous, laterally without small appendages..

................................ M. rottboellioides

Figures

Fig. 10 Mnesithea rottboellioides (R.Br.) de Koning & Sosef. a. Pedicelled spikelet; b. joint and pedicelled spikelet (all: Van Steenis 18081, L).