Two new species of Morinda ( Rubiaceae ) from Sumatra and Borneo

Two new species of Morinda from Sumatra and Borneo, M. lanuginosa and M. wongiana, are described and illustrated. The morphological comparison of the new taxa with similar species in the genus is also discussed.


INTRODUCTION
Morinda L. is one of the 611 genera belonging to family Rubia ceae Juss.(Govaerts et al. 2009).The genus consists of c. 90 species (Mabberley 2008), and is distributed widely in the tropics and subtropics, but absent from Northern and Southern Africa, the Mediterranean region, Arabian Peninsula, Western Asia, New Zealand and Southern South America (Govaerts et al. 2009).
The presence of raphide idioblasts, valvate corolla aestivation and often heterostylous flowers points to a position within subfamily Rubioideae (Robbrecht & Manen 2006).It has been grouped in the tribe Morindeae together with Appunia Hook.f., Coelospermum Blume, Gynochthodes Blume, Pogonolobus F.Muell. and Syphonandrium K.Schum.(Razafimandimbison et al. 2008).Igersheim & Robbrecht (1993) discussed the circumscription of the Morindeae and proposed to restrict the tribe to representatives with a "bicarpellate gynoecium comprised of a common style with two stigma lobes, and two biovulate locules".Razafimandimbison et al. (2009) considered that within the tribe Morindeae, the type genus Morinda is traditionally and currently circumscribed based on its head inflorescences and syncarpous fruits.These characters are also present in other Rubiaceae genera, especially Schradera, which can look similar to Morinda.
In the fruiting stage, Schradera resembles Morinda but can be distinguished by not having true syncarps.The fruiting heads of Morinda consist of fused fruitlets whereas the fruitlets of Schra dera are not fused.In head inflorescence, ovaries of neighbouring flowers in Morinda are united or at least closely pressed together whereas ovaries of adjacent flowers of Schradera in close contact with each other but not fused (Puff 2007).

DESCRIPTIONS 1. Morinda lanuginosa
Etymology.The specific epithet for this species is derived from the latin word lanuginosus, which means woolly, in reference to the dense woolly hairs along the inner surface of the corolla tube of the species.
Etymology.The specific epithet honours Prof. Dr. K.M. Wong, a botanist from the University of Malaya (Malaysia), who revised Morinda in the Malay Peninsula.
Habitat & Ecology -Found in rain forest and secondary vegetation, a few metres above sea level.Note -On Buwalda's labels, this is noted as shrub.A morphological comparison of this plant with related species however shows that most characters match with those of climbing species.This species is similar to M. rigida Miq.leaf texture and inflorescence shape but can be distinguished from the latter because the surface of young branchlets, leaves, midribs, petioles, peduncle, outer calyx limb surface of male flowers and fruiting head stalks is always glabrous.The calyx limb and fruiting head stalks are also considerably longer ((1.75-)2-3.5mm resp.(6-)7.25-24mm) than in M. rigida (0.75-1.5 mm resp.3-6 mm).Only four specimens are known in this study, one with fallen corollas (H.Hallier 1048), two with mature fruit (H.F.Sun 9937 and Jaheri 1893) and one with immature fruit (P.Buwalda 6223).The distinction of the floral types is not always easy, especially for the inexperienced.Therefore, more material is needed to clarify floral morphology of this species.

Fig. 1
Fig. 1 Morinda lanuginosa Suratman.a. Branch habit; b. lower leaf surface showing venation (note that domatia are absent in the axils of secondary veins); c. flowering head with flower buds; d. mature open male flower; e. longitudinal section of inner surface of flower showing woolly hairs; f. dorsifixed stamen (a -c: P. Buwalda 6744; d-f: Berkhout 1507).