Memecylon impressivenum 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 : 348

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

( Fig. 6 )

Similis M. inalato Jacq.-Fél. a quo ramulis junioribus anguste quadrialatis non teretibus, foliis parvioribus ad apices late obtuseque acuminatis, venis transversis in paginis superioribus foliorum conspicue impressis, pedunculis brevioribus, floribus subsessilibus differt.

TYPUS. — Madagascar. Antsiranana province, Masoala peninsula, canyon of the Ampanavoana river , 15°40’45”S, 50°09’35”E, alt. c. 150 m, understory of evergreen rain forest, relatively dry site on small spur ridge west of river, 8.XII.2001, Stone et al. 2406 (holo-, CAS; iso-, CAS, G, K, MO, P, TAN, TEF, UC, US, WAG) .

DESCRIPTION

Evergreen shrub 2-3 m high; branchlets quadrangular and narrowly 4-winged when young (the wings ± straight to slightly crisped), becoming terete with age and thickened at the nodes; internodes 2-4 cm long. Leaves subcoriaceous, sessile or nearly so (petioles up to 1 mm long), dark green and somewhat shining on the upper surface, paler and dull beneath, rugose on both surfaces (when dry); blades elliptic-ovate, 3.5-5.5 cm long, 1.5- 2.5 cm wide, gradually rounded toward the base then narrowly subcordate above the petiole, apex broadly acuminate (the acumen c. 5 mm long, obtuse); mid-nerve impressed on upper and lower surfaces; transverse veins oriented at an oblique angle relative to the mid-nerve, conspicuously impressed on the upper surface, obscure on the lower; lateral nerves situated 1-1.5 mm from the margin; young leaves strongly violaceous. Cymes umbelliform, 1- 5-flowered, axillary and solitary but often opposite, often hidden beneath the leaves; peduncles filiform, 1-2 cm long, quadrangular and narrowly 4-winged; bracts lanceolate, 1-2 mm long, the bracteoles similar but smaller. Flowers subsessile, ochroleucous; hypantho-calyx campanulate, c. 2 mm long and 2.8 mm wide; calyx shallowly 4-lobed, the lobes broadly rounded. Corolla rounded and apiculate in bud; petals suborbicular, 2 mm long, 1.5 mm wide, apiculate, the margins scarious. Anthers 1.5 mm long, the connective shortly conical and ± incurved but lacking a dorsal gland, the pollen sacs occupying more than half the length on the ventral side; filaments c. 1.5 mm long. Style c. 3 mm long. Fruits not seen.

REMARKS

This species is known only from the type collection. The long, slender peduncles and anthers lacking a dorsal gland suggest a close relationship with M. alatum Aug.DC. , M. mocquerysii Aug.DC. , and M. inalatum . It is perhaps most similar to M. inalatum which is based on a fruiting specimen (Capuron SF-24056, P) from Toamasina province, Analalava forest on laterite west of Foulpointe (approximately 230 km to the south). A recent collection from the eastern Masoala peninsula, Aridy 123 (CAS, MO, P, TAN), is tentatively included in the circumscription of M. inalatum , although it differs from the type in some details (i.e. the somewhat smaller leaves with transverse veins obscure and the peduncles which are less than 3 cm long and quadrangular in cross-section). Aridy 123 has mainly fruits, but the specimen at CAS also has flower buds that are identical to those of M. impressivenum .

Another species with umbellate cymules on long, axillary peduncles is the Tanzanian M. cogniauxii Gilg , under which M. mocquerysii was previously placed as a synonym (Jacques-Félix 1985a: 432). While these two species superficially resemble one another, their branchlets and floral characteristics are remarkably different, and phylogenetic analyses of DNA sequences place M. cogniauxii in a separate group along with most of the other east- African species sampled thus far ( Stone 2004 and unpubl. data).

Figures

FIG. 6. — Memecylon impressivenum R.D.Stone: A, habit; B, inflorescence with flower buds; C, petal; D, anther and part of filament. Stone et al. 2406. Scale bars: A, 3 cm; B, 2 mm; C, D, 1 mm.