Memecylon pterocladum R.D.Stone, 2006

Stone, Robert Douglas, 2006, New species of Memecylon L. and Warneckea Gilg (Melastomataceae) from Madagascar and Mayotte, Adansonia (3) 28 (2), pp. 337-358 : 342-344

Memecylon pterocladum R.D.Stone , sp. nov.

( Fig. 3 )

A M. dolichophyllo Naudin ramulis junioribus valde quadrialatis non teretibus, petiolis perfecte nullis, laminis ad bases conspicue cordatis, venis transversis ad costam plus minusve perpendicularibus non obliquis, pedicellis brevioribus differt.

TYPUS. — Madagascar. Toamasina province, south of Soanierana-Ivongo, Sahavolamena forest , on laterite, 21.XII.1967, Capuron SF-28110 (holo-, P, barcode no. 257960; iso-, P) .

PARATYPES. — Madagascar. Toamasina province, 7.5 km south of Ambila-Lemaitso, Andavakimena forest near Lac Andobobe , 18°54’S, 49°07’20”E, alt. 10 m, deeply shaded understory of littoral forest on sand, 14.XI.2001, Stone et al. 2385 ( CAS, MO, P, TAN) . — Toamasina province, 8 km west of Foulpointe [Mahavelona], Analalava forest , 17°42’30”S, 49°26’50”E, alt. 60 m, north-facing slope in deeply shaded understory of evergreen rain forest on laterite, 17.XI.2001, Stone et al. 2391 ( CAS, G, K, MO, P, TAN, TEF, US) .

DESCRIPTION

Evergreen shrub or small tree up to 5 m high; branchlets virgate, leafy toward the apex, up to 4 mm in diameter; young branchlets strongly 4-winged (wings greater than 1 mm wide), the older rapidly excoriating and becoming terete, thickened at the nodes; internodes 3-12 cm long. Leaves subcoriaceous, sessile, yellowish green on the upper surface (when dry), bright to pale green or violaceous on the lower, finely rugose on both surfaces; blades broadly lanceolate, 10-30 cm long, 3.3-7 cm wide, rounded and narrowly cordate at base, attenuate and acute at apex; only the mid-nerve clearly visible, canaliculate on the upper surface, prominent on the lower, very wide at the base (up to 4 mm), becoming progressively narrower toward the apex; transverse veins obscure on the upper surface, ± visible on the lower, perpendicular or slightly oblique relative to the mid-nerve, ± straight or occasionally forked; lateral veins situated 2-3 mm from the narrowly revolute margin; young leaves strongly violaceous. Cymes contracted, ± sessile, 1-3-flowered, fascicled at the nodes below the current leaves; bracts broadly ovate, auriculate at base, ± cucullate, 0.8 mm long, persistent; bracteoles similar but smaller. Flowers at anthesis not seen, in bud with hypantho-calyx obconic, the margin 4-lobed, the lobes broadly triangular and apiculate, the corolla acute. Fruits globose, 8 mm in diameter, on pedicels c. 1-2 mm long; calycinal crown 1 mm long, spreading, the margin sinuate and 4-microdentate; epigynous chamber deep, lacking radial partitions.

REMARKS

The type is a fruiting specimen that was previously cited but not described in detail (Jacques-Félix 1985b: 36). In addition there are two recent collections including one (Stone et al. 2391) with flower buds but no fully developed flowers. The prominently winged young branchlets of M. pterocladum resemble those seen in M. capuronii Jacq. -Fél., M. pterocarpum H.Perrier , and M. fernandesiorum Jacq. -Fél. The new species is also somewhat similar to M. subsessile H.Perrier , which notably differs in its slender, terete branchlets; papyriferous, short-petioled leaves that are smaller and strongly acuminate at the apex; and axillary cymes.

A collection of M. dolichophyllum (Capuron SF- 28114, P) from the type locality of M. pterocladum suggests that the two species are at least partially sympatric. Their fruits are identical; they also resemble one another in having subcoriaceous leaves and cymes borne at the nodes below the current leaves. They are however quite different since M. dolichophyllum has petiolate leaves that are merely rounded (not cordate) at the base and with transverse veins oblique; its fruiting pedicels are also 3-4 mm long.

Figures

FIG. 3. — Memecylon pterocladum R.D.Stone:A, habit; B, detail of young branchlet and leafy node;C, inflorescence with flower buds; D, fruit. A, D, Capuron SF-28110; B, Stone et al. 2385; C, Stone et al. 2391. Scale bars: A, 5 cm; B, 2 cm; C, 1 mm; D, 5 mm.