Memecylon sejunctum 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 : 340-342

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

( Fig. 2 )

Affinis M. infuscato Jacq.-Fél. sed habitu plus minusve fruticoso, laminis foliorum brevioribus angustioribusque differt.

TYPUS. — Madagascar. Toamasina province, Parc national d’Andasibe-Mantadia , 14 km by road past the graphite mine, 18°53’S, 48°27’30”E, alt. 1100 m, short-statured, relatively open forest on steep, west-facing slope, 13.XI.2001, Stone et al. 2380 (holo-, CAS; iso-, G, K, MO, P, TAN, TEF, UC, US; flowers in spirit collection at CAS) .

PARATYPES. — Madagascar. Toamasina province, near Andasibe, Mantadia forest , beyond graphite mine, 18°55’S, 48°25’E, alt. 950-1150 m, 7.XI.1994, McPherson & Van der Werff 16529 ( CAS, MO) . — Type loc., 13.XI.2001, Stone et al. 2379 ( CAS, G, K, MO, P, TAN, WAG; flowers in spirit collection at CAS) . — Toamasina province, Parc national d’Andasibe-Mantadia on trail to Belle Vue and eastward along ridgetop, 18°47’42”S, 48°25’46”E, alt. 910-1050 m, wet mossy forest, 25.III.2004, Almeda et al. 8764 ( CAS) . — Antsiranana province, Vohemar [Iharana] sub-prefecture, Daraina rural district, Ankijabe village , Binara forest , 13°15’S, 49°37’E, alt. 1050 m, low forest on exposed ridge, 4.XI.2001, Gautier & Ravelonarivo 4023 ( CAS, G) . — Same locality, alt. 910 m, low open dry forest on ridge, 10.XI.2001, Gautier & Ravelonarivo 4159 ( CAS, G) .

DESCRIPTION

Evergreen large shrub or many-branched small tree up to 6 m high; youngest branchlets quadrangular and narrowly 4-winged, the older becoming terete and thickened at the nodes; internodes (1-)1.5-2.5(-3) cm long; bark whitish.Leaves coriaceous, dark green on the upper surface, paler green on the lower, finely granular-rugose on both surfaces; petioles 2-4 mm long; blades narrowly elliptic to oblanceolate, 3- 5 cm long, 1.2-1.9 cm wide, narrowly cuneate at base and decurrent with the petiole, apex obtuse to rounded and often retuse; mid-nerve impressed on upper surface, somewhat prominent on the lower; transverse veins obscure; margins slightly revolute. Cymes ± contracted, less than 1 cm long, 1-4-flowered, solitary or fasciculate in the axils and at the nodes below the leaves, sessile or with a peduncle up to 1.5(-2) mm long; bracts up to 0.8 mm long, squamiform, several pairs imbricated at the base of the pedicels, persistent.Flowers on pedicels 1.5-2 mm long; hypantho-calyx campanulate, 2mm long, 3 mm wide, the margin 4-denticulate. Corolla acute in bud; petals violet (or white), triangular-acuminate, 3.5-4 mm long, 3 mm wide, apex acute, base sessile (not clawed), broadly rounded to shallowly cordate. Anthers 2.5-3 mm long; connective ± straight (not incurved), the extremity long-acuminate, the pollen sacs lateral (anterior), the dorsal surface depressed by a gland situated near the pollen sacs; filaments 4 mm long. Style 4.5-6 mm long; ovules 12. Fruits (immature) globose, c. 5 mm in diameter, the calycinal crown c. 1 mm long, erect.

REMARKS This new species is known from east-central and northeastern Madagascar (the Moramanga and Daraina districts respectively). It is closely related to M. infuscatum , a small tree found along the eastern coast from Masoala peninsula southward to near Nosy Varika (Fianarantsoa province). Similarities between the two species include leaf apices rounded and often retuse; inflorescences contracted and borne mostly at the defoliated lower nodes; bracts imbricate, squamiform, and persistent; hypantho-calyx campanulate with margin conspicuously 4-dentate; corolla acute in bud; and anther gland situated near the thecae. They differ not only in habit and leaf dimensions but also in distribution and ecology (littoral forest for M. infuscatum , montane forest for M. sejunctum ). The fruits of M. infuscatum were first described as globose and 20 mm in diameter (Jacques-Félix 1985b), but with additional collections it is evident that they are really much smaller (c. 5 mm) and more-or-less identical to those of M. sejunctum . The fruiting specimen SF-16639 (MO, P), on which the earlier description was based, should no longer be included in M. infuscatum although its proper taxonomic disposition is unknown. The leaves of M. sejunctum superficially resemble those of M. bakerianum Cogn. , a species mainly of

Madagascar’s central plateau that has been collected several times in the montane forest region (once near Moramanga, Andriatsiferana et al. 2173, MO, P). Memecylon bakerianum differs however by its cymes with peduncles 10-15 mm long and deciduous bracts, larger flowers with calyx margin sinuate and anther gland situated medially, and leaves with transverse veins usually visible on the lower surface. Another narrow-leaved species occurring in the same region is M. myricoides Naudin , but its habitat is always bordering streams, and the cymes are mainly axillary, the peduncles are 10 mm long, the calyx is truncate-margined, and the anthers lack a dorsal gland.

Figures

FIG. 2. — Memecylon sejunctum R.D.Stone: A, habit; B, inflorescence just before anthesis; C, petal; D, stamen. Stone et al. 2380. Scale bars: A, 3 cm; B, 2 mm; C, D, 1 mm.