Mnesithea striata (Nees ex Steud.) 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 : 287-289

10. Mnesithea striata (Nees ex Steud.) de Koning & Sosef — Fig. 11

Mnesithea striata (Nees ex Steud.) de Koning & Sosef in Veldkamp et al. (1986) 292. — Rottboellia striata Nees ex Steud. (1854) 361; Hack.(1889) 302 (incl. ssp. genuina Hack. , nom. inval., var. glabrior Hack. , nom.inval.). — Coelorachis striata (Nees ex Steud.) A. Camus (1921) 197, pro comb. — Manisuris striata (Nees ex Steud.) Kuntze (1891) 779. — [ Rottboellia rottboellioides (R.Br.) Druce var. striata (Nees ex Steud.) Roberty (1960) 76, comb. inval.]. — Lectotype: Wallich 8877-C (Gomez) (holo P; K, W), designated by Veldkamp et al. (1986: 292).

Rottboellia striata Nees ex Steud.var. pubescens Hack.(1889) 302. — Coelorachis striata (Nees ex Steud.) A.Camus var. pubescens (Hack.) Henrard (1941) 519; Bor (1960) 121,isonym. — Type: Hook.f.& T.Thomson s.n. (holo W; K, L).

Rottboellia merguensis Hook.f. (1896) 158. — Mnesithea merguensis (Hook.f.) A. Camus (1919) 59. — [ Rottboellia corymbosa L.f. subvar. merguensis (Hook.f.) Roberty (1960) 65, comb. inval.]. — Lectotype: Helfer 457 (holo K, fragm. in L; G), designated by Roberty (1960, ‘437’), holotype designated here.

Coelorachis striata (Nees ex Steud.)A.Camus var. laevis Stapf ex Bor (1960) 121. — Type: Wallich 8877-A (holo K), erroneously cited as ‘ 8877-D ’ by Bor.

Plants perennial. Culms 1.5–2.5 m long. Cataphylls ovate to ovate-oblong, 5–24 by 2–9.5 mm, glabrous to puberulous, apex acute to acuminate. Nodes glabrous to puberulous. Sheaths glabrous to hairy, margin glabrous to pilose. Ligule 1–4.5 mm long, glabrous or margin setose. Contra-ligule absent or present, glabrous. Blades flat to folded, 15–43 cm by 6–35 mm, margins glabrous to pectinate at base, glabrous to hairy on both sides, glabrous behind the ligule, smooth. Peduncles solitary or paired, glabrous to hairy. Spatheoles 3–5.5 cm long. Spikes 2.5–4 cm by 1.8–2.2 mm. Spikelets in the lower part in triads, or all paired. Joints 5.5–6.5 mm long, glabrous, smooth to ciliolate at base. Callus glabrous to ciliolate. Sessile spikelet 5.8–6.8 mm long (incl. callus), longer than the joint. Lower glume convex, ovate-oblong, glabrous, coriaceous, with lines of small slits, yellowish with purplish margins, 7-nerved, apex winged. Upper glume boat-shaped, ovate-oblong, 5.2–6.1 mm long, glabrous, 3–4-nerved, not anastomosing, margin infolded, apex obtuse to acute. Lemmas ovate-oblong, glabrous to ciliolate along the margin, apex rounded to acute; first lemma paleate, 4.8–5.9 mm long, 2–3-nerved; second lemma 3-nerved. Paleas 2-nerved, glabrous or with ciliolate margin; first palea ovate-lanceolate, 2.9–3.4 mm long; second palea ovate-oblong, 2.3–2.8 mm long. Anthers 1.4–1.6 mm long. Pedicel free to adnate to the joint, 5.4–5.8 mm long, glabrous to pubescent. Pedicelled spikelets reduced to 2 glumes, laterally to dorso-ventrally flattened, 1–2 mm long. Lower glume chartaceous, glabrous to margins ciliolate, apex winged. 2n = 36.

Distribution — Burma (Mergui) to S Vietnam and S China (S Yunnan); Thailand (N: Chiang Mai, Chiang Rai, Lamphun; NE: Khonkaen; SW: Kanchanaburi; Peninsular: Phangnga). Mentioned for Singapore by Wallich and so cited by others, but Wallich 8876 is M. mollicoma . It is erroneously cited as the type of M. striata by Roberty (1960).

Noltie (2000: 829, t. 62k) reported the species for ‘Terai’, an area along the S border of Bhutan with Assam.

Habitat — Sunny places, old clearings, in the area between the deciduous dipterocarp oak-forest and a bamboo hardwood zone, moist savannah on clay, dry evergreen or mixed ( Quercus ) forest, along the road, granite bedrock, 25–1325 m altitude, locally common.

Notes — The species is best recognized by the glabrous lower glume of the sessile spikelets without appendages and with lines of small slits (which, however, are nearly absent in var. laevis Bor ). For differences with M. helferi , see there.

The reasons for the lectotypification of M. striata and the reduction of the varieties has been discussed by Veldkamp et al. (1986: 292).

Part of Helfer 457 (syntype of M. merguensis ) has pedicelled spikelets on two-jointed pedicels. One joint had four sessile and two pedicelled spikelets. Some other joints had two sessile and one pedicelled spikelets. The lower glumes have some pusticules with hairs .

Two collections from Thailand (Van Beusekom et al. 3597 (L, P) and Iwatsuki et al. T-10929 (L) have the pedicel fused to the joint in the lower part to completely so, while in the other specimens seen they were usually completely free.

Geesink & Santisuk 5004 (L, P) has lower glumes with pusticules on the keels. Tran Van Hing 196 has some joints with three sessile and two pedicelled spikelets. This specimen has hairy culms, sheaths and blades. It is the only collection seen from Vietnam, all other references seem to refer to M. cancellata (q.v.).

Differs from the Malesian / Thai congeners in: Culms 1.5–2.5 m long. Sessile spikelet 5.8–6.8 mm long (incl. callus); upper glume 5.2–6.1 mm long.

Most similar are M. cancellata and M. glandulosa :

1. Culms 0.4–1.1 m long. Sessile spikelet 4.3–5.8 mm long (incl. callus); lower glume cancellate; upper glume 3.3–5.1 mm long............................ M. cancellata 1. Culms 1.5–2.5 m long. Sessile spikelet 5.8–6.8 mm long (incl. callus); lower glume with longitudinal lines of small slits; upper glume 5.2–6.1 mm long.............. M. striata 2. Sessile spikelet 3.8–5.5 mm long (incl. callus); lower glume smooth, laterally with small appendages; upper glume 2.8– 4.9 mm long......................... M. glandulosa 2. Sessile spikelet 5.8–6.8 mm long (incl. callus); lower glume smooth, laterally without small appendages and with lines of small slits; upper glume 5.2–6.1 mm long.... M. striata

Figures

Fig. 11 Mnesithea striata (Nees ex Steud.) de Koning & Sosef. a. Sessile spikelet; b. pedicelled spikelet (all: Van Beusekom et al. 3597, L).