Mnesithea laevis var. laevis

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 : 284-285

a. var. laevis — Fig. 7

Mnesithea laevis (Retz.) Kunth (1829) 154. — Rottboellia laevis Retz.(1783) 11. — [ Thyridostachyum laeve (Retz.) Nees ex Steud. (1841) 474, 685, nom. inval.]. — Ophiuros laevis (Retz.) Benth. (1881) 69. — [ Rottboellia corymbosa L.f. subvar. laevis (Retz.) Roberty (1960) 65 (‘var.’), 68, comb. inval.]. — Type: Koenig s.n. (holo LD; fragm. K).

Rottboellia perforata Roxb.(1798) 43,t. 182. — Hemarthria perforata (Roxb.) Kunth (1829) 153. — Ophiuros perforatus (Roxb.) Trin. (1824) 19, t. 1, f. 2, 3; (1832) 246. — Mnesithea perforata (Roxb.) Haines (1924) 1060, nom. superfl. — Type: Herb. Roxburgh s.n. (holo BM; Icon. Ined. 862, CAL, K ≡ Roxb. (1798) t. 182; Wallich 8873-A, K (microfiche IDC 7394)).

Diperium cylindricum Desv. (1831a) 180, t. 9, f. 3; (1831b) 76, t. 8, f. 3. — Type: Herb. Desvaux (holo P; perhaps in ANG, FI, G, M, PC).

Mnesithea laevis (Retz.) Kunth var. hirta Jansen (1953) 308. — Type: Eyma 361 (holo BO; L).

Heteropholis cochinchinensis auct. non Clayton var. cochinchinensis .

Culms 0.2–1.2 m long. Cataphylls ovate to ovate-oblong, 2 –15 by 1.3–3 mm. Nodes glabrous to setose. Sheaths glabrous to sparsely hairy, margin glabrous to pilose. Ligule 0.2–1.8 mm long. Blades 11–35 cm by 1–4.5 mm, margins at base glabrous, glabrous to hairy above, glabrous to setose behind the ligule. Peduncles glabrous to hairy. Spatheoles 4.5–6.5 cm long. Spikes 2.5–10 cm by 1.5–3 mm. Spikelets usually in triads or paired (upwards, in depauperate specimens only the most basal group a triad, or, very rarely, all paired). Joints 4.4–6.5 mm long. Sessile spikelet 4–5.6 mm long (incl. callus); lower glumes flat to convex, smooth, greenish yellow, 4–5-nerved, apex rounded, winged or not; upper glume of boat-shaped to concave, 3.9–5.1 mm long, 2–3-nerved, apex obtuse to acute; first lemma 3.8–4.2 mm long, 3–4-nerved; paleas 2-nerved; second palea ovate-oblong to ovate-lanceolate, 2.9–3.6 mm long. Anthers 1.8–2.5 mm long. Pedicel 4.4–5.8 mm long. Pedicelled spikelets 0.2–0.4 mm long. 2n = 18.

Distribution — Pakistan to Sri Lanka, Burma, Thailand (N: Chiang Mai, Sukhothai, Nakhon Sawan, Kamphaeng Phet; E: Chaiyaphum, Nakhon Ratchasima, Buri Ram; SE: Chon Buri, Kanchanaburi; Peninsular: Songkhla), Laos (Champasak, Saravan), Malesia: Java (Ceribon, Surabaya, Besuki), Madura, Celebes (Rapang), Bali. The variety has been recorded for Laos, Cambodia and S Vietnam, but material from these countries as far as we have seen it all belonged to var. cochinchinensis . The genus was not recorded for Afghanistan by Bor (1970) although it is a country cited for this species and where it possibly may occur.

Habitat — On rather open grassy slope, dry savannah forest, sunny places, in a dipterocarp-savannah area, along the road, stony soil, up to 1500 m altitude.

Ecology — Beumée (1927: 419) reported the presence of myrmecochory.

Uses — Readily eaten by cattle, at least when young. Little valued by the Javanese because of its relative little yield of rather tough leaves mixed with tough culms. Analyses showed a very little nutritional value with an excess of fibre ( Backer 1950: 177, sub M. laevis ).

Notes — The species is distinct by the smooth, unappend- aged lower glume of the sessile spikelets , the adnate pedicel, and the much reduced, small pedicelled spikelets.

Jansen (1953) described a var. hirta on a Celebes collection which notably differed from the generally glabrous Java material by its rather dense bulbous-based bristly indument of the blades and peduncles. Specimens variable in this feature have been seen from Sri Lanka (Clayton 5845, Davidse 7598, Lazarides 7262), while others from Thailand (Van Beusekom & Phengkhlai 1192, Maxwell 75-433) were intermediary. It therefore seems to us that a taxonomic distinction for such hairy specimens cannot be maintained.

According to the general literature M. laevis would have spikelets in triads. In fact this is not always so. Within the same spike both triads and paired spikelets occur, with a general tendency for the triads to be present at its base and the pairs more upwards. Sometimes the most basal spikelets are paired, followed by triads, and distally again paired. This basal grouplet usually persists after the spike has broken up, and, when consisting of paired spikelets, may cause confusion in identification. In poorly developed specimens the triads may be very few to even totally absent (cf. Kievits 1543, see the discussion by Veldkamp et al. (1986) 284). The distinction against the var. cochinchinensis then becomes very difficult. The var. laevis seems to be distinct by being more robust (60–170 cm tall against up to 50 cm in var. cochinchinensis ), while it grows in less disturbed places. The general distribution is also different (see map in Veldkamp et al. 1986: 285).

In Van Steenis 6648 and 7532 from Ceribon the terminal joints have one sessile and two pedicelled spikelets, the more ‘normal’ type of triad often found in the Andropogoneae . The first collection, moreover, has doubly pedicelled spikelets, i.e. there is an additional internode between the pedicel and the spikelet, which then reaches to 0.5–0.67th of the next higher joint fitting into a shallow excavation there .

Differs from the Malesian / Thai congeners in: Culms 0.2–1.2 m long. Sheaths glabrous to sparsely hairy. Blades margins at base glabrous. Pedicelled spikelets reduced to 1 small scale, 0.2–0.4 mm long.

Most similar is var. cochinchinensis (see key).

Figures

Fig. 7 Mnesithea laevis (Retz.) Kunth var. laevis. a. Sessile spikelets and pedicelled one; b. joint (all: Backer 20193, L).