REVISION OF THE GENUS CLEIDION (EUPHORBIACEAE) IN MALESIA

A revision of the Malesian species in the genus Cleidion is presented. Cleidion javanicum is shown to be the correct name for the widespread type species (instead of the name C. spiciflorum). A new species, C. luziae, resembling C. javanicum, is described from the Moluccas, New Guinea and the Solomon Islands. In addition, C. salomonis is synonymised with C. papuanum and C. lanceolatum is treated as a variety of C. ramosii. In total 7 Malesian Cleidion species are recognized. Cleidion megistophyllum from the Philippines cannot reliably be confirmed to belong to the genus due to lack of information and specimens and is treated as a doubtful species.


INTRODUCTION
Cleidion is a pantropical genus belonging to the large angiosperm family Euphorbiaceae s.s. It was described by Blume (1826), who included a single species C. javanicum 2 . The first revision was made by Müller Argoviensis (1865,1866). His work was followed by the comprehensive treatment of Pax & Hoffmann (1914), which included 17 species. Pax & Hoffmann excluded the section Discocleidion Müll.Arg. which differs from Cleidion by the presence of a staminate and pistillate disc (in Cleidion a disc is absent), stipellate and palmatinerved leaves (in Cleidion the leaves are non-stipellate and pinnatinerved), and differences in anther type. Currently the genus Discocleidion (Müll.Arg.) Pax & K. Hoffm. is considered as a member of the tribe Bernardieae, while Cleidion is placed in the tribe Acalypheae (Webster, 1994b;Radcliffe-Smith, 2001).
All species of the genus Cleidion share a peculiar, unique anther type. The anthers are dorsifixed, the connective continuing as an inflexed apiculum. The anthers consist of 4 cells, with 2 superimposed cells at each side, which are confluent after opening introrsely in a cruciate manner ( Fig. 6.2e). This special anther type does not occur in any other Euphorbiaceae genus. Additional typical (although not unique in the family) characters for the genus are the presence of extra-floral nectaries on both leaf surfaces and deeply split (bipartite) stigmas. Other features for Cleidion include: growth form shrub or tree; alternate, simple and penninerved leaves; petioles with an adaxial groove; axillary, racemiform or paniculate (or single-flowered when pistillate) inflorescences; small, pedicellate flowers without disc and petals; many anthers arranged in vertical series; mostly a 3-locular ovary; and capsulate, lobed fruits.
Cleidion is currently placed in the subtribe Cleidiinae (subfamily Acalyphoideae; tribe Acalypheae) with Sampantaea Airy Shaw and Wetria Baill. (Webster, 1994b;Radcliffe-Smith, 2001). These two Asiatic genera, like Cleidion, have extra-floral nectaries on both leaf surfaces and deeply split stigmas. Radcliffe-Smith (2001) also mentions globose, vermiculate pollen as a unifying character for the subtribe. However, according to Takahashi et al. (2000), the tectum of Wetria pollen deviates from that of Cleidion and Sampantaea, resembling more genera from other subtribes (Adriana and Ricinus; subtribes Adrianinae and Ricininae, respectively). The monophyly of the subtribe is thus disputable. Also, the monophyly of Cleidion itself remains to be tested, although the unique anther type can be seen as a tentative synapomorphy for the genus.
In this paper we report a revision of the Malesian species of Cleidion. Non-Malesian material of these species was also examined, and a critical look was given to the other Cleidion species occurring in nearby areas. Seven species are recognised, of which one is described as new. Two species are synonymised, and one regarded as doubtful. In Malesia only one species, C. javanicum, is widespread and relatively common with more than 300 collections examined for this study. In contrast, four species are represented by 5-30 collections, and three species by a single collection only.

NOTES ON CHARACTERS AND MORPHOLOGY
Descriptions and measurements are based solely on dry herbarium material and accompanying field notes. Colours presented indicate the fresh state inferred from field notes unless stated otherwise. The small organs were measured within a precision of 0.25 mm excluding anthers (precision 0.1 mm). To describe leaf venation, the term ʻnerveʼ is used for veins branching from the midrib (= secondary veins), and the terms ʻveinsʼ and ʻveinletsʼ for the next two orders of venation (= tertiary and quaternary veins). The leaf nerve counts exclude the faint nerves at the apex. When measuring the staminate bud diameter, the frequently occurring premature buds were omitted, and only the largest buds were taken into account. The parts of pistillate inflorescences (excluding the ovary) do not considerably enlarge during fruit development, therefore, only a single measurement was taken.
Most of the Malesian Cleidion species are shrubs or small trees, only C. javanicum and C. luziae regularly exceed 10 m in height. Although the inferences made from herbarium collections and field notes are tentative, C. papuanum seems to have a deviating habit: a Schopfbaum-like unbranched or scantily branching shrub or treelet with the leaves grouped at the stem apices.
The distribution of the sexes is somewhat difficult to determine in Cleidion. Cleidion javanicum and C. papuanum are predominantly dioecious, although a few specimens have both staminate and pistillate inflorescences or aberrant bisexual inflorescences.
The specimens of most of the other species can be both uni-or bisexual. This either indicates the occurrence of both uni-and bisexual individuals, or the separation (spatial and/or temporal) of two sexes within a plant.
Indumentum and granules-The indumentum in Malesian Cleidion consists of simple, short (rarely exceeding 0.5 mm in length) relatively stiff hairs. Most typically the hairs are sericeous (bent towards the apex of organs with an angle between 0° and 45°), but hirsute (either strictly erect or variably oriented) hairs also occur. The density of the indumentum is roughly quantified by the terms glabrous, subglabrous (only a few occasional hairs), sparsely hairy and densely hairy (hairs covering most of the surface).
The surfaces of most Cleidion species are granulate, i.e., dotted with small round protuberances. This character is most clearly seen on the upper surface of relatively young leaves; on other plant surfaces (i.e., mainly young branches, stipules, bracts and sepals) granules can be variably indistinct or absent.
According to a preliminary anatomical study (data not shown), the granules on the leaf of C. ramosii are caused by large druses (star-shaped crystals) in the palisade parenchyma. Crystals can also occur in the leaves of the non-granulate species studied (C. javanicum), but they are too small to be seen as external protuberances. It is not known how well granulate surfaces can be seen in fresh plants, therefore, this character might be a drying artefact and thus only visible in dry herbarium material.
Inflorescences-The racemiform staminate inflorescences of Malesian Cleidion species consist of an unbranched rachis with a cluster of pedicellate flowers at each node (outside Malesia Cleidion can also have branching paniculate inflorescences). Four types can be distinguished on the basis of the flower production capacity and the structure of the flower clusters ( Fig. 6.1). A few species (C. luziae and Vietnamese C. bracteosum) have  true racemes with only one flower per node. In some other species (e.g., C. javanicum), the node produces several flowers, resulting in a fasciculate cluster (individual flowers and pedicels still being separate). If flower production continues for a longer period, a dense, glomerulate cluster develops, consisting largely of bracteoles and pedicels of fallen flowers. In the fourth type, seen in C. papuanum, the cluster is branched and slightly elongated in form. When using the cluster types for species identification, it is important to realise that the glomerulate and elongated clusters form over time and, therefore, can still look fasciculate in younger inflorescences.
Most Malesian species have racemiform pistillate inflorescences with each node producing one, or sometimes two or three, flowers. However, quite often, some of the bracts remain sterile. The strictly single-flowered inflorescences of C. javanicum and C. luziae can thus be regarded as a further reduction, in which only one flower develops. Cleidion luziae has a somewhat intermediate inflorescences with persistent bracts and, usually, an abscission zone in the terminal pedicel, whereas in C. javanicum bracts are early caducous and the abscission zone is absent. The reduction in the number of flowers is associated in these two species with the increase in the size of the seeds, presumably indicating a shift in reproduction strategy. Shrubs to trees; mono-or dioecious; very young branches somewhat angular when dry, older branches terete, glabrescent. Indumentum consisting of simple, short hairs, sericeous (to hirsute with erect or variably oriented hairs), most parts glabrous to only sparsely hairy (the inside of organs always (sub)glabrous); granulate surfaces absent to present. Stipules triangular, usually caducous, base and central part thickened, margin entire and sometimes hairy, apex acute. Leaves alternate, simple; petiole with adaxial groove, usually basally and apically pulvinate, sometimes with 2 raised glands at apex; blade (ovate to) elliptic to obovate, symmetric, papery (to somewhat coriaceous in C. papuanum), margin subentire to crenate to serrate (tooth size varying within a species), with a gland in each tooth, apex usually acuminate; both surfaces with small roundish extra-floral nectaries (= macular glands; in C. moniliflorum only on lower surface), on upper surface mainly grouped loosely near the base, on lower surface mainly in the basal half of the blade and often more or less in lengthwise rows; upper surface usually darker green than lower surface; venation pinnate, ± flat above, raised beneath, nerves looped and closed near the margin, veins (irregularly) scalariform to reticulate, veinlets reticulate. Inflorescences axillary, single (or in C. moniliflorum the staminate ones ramiflorous and often 2 together), unisexual, racemiform (to paniculate outside Malesia) in both sexes to single-flowered when pistillate, rachis often with longitudinal ridges when dry, staminate nodes with 1 flower only or bearing several flowers in a fasciculate to glomerulate (to slightly elongated and branched) cluster, pistillate nodes with 1-3 flowers (or sometimes remaining sterile); bracts triangular to ovate, base and central part thickened, margin entire, often hairy, apex acute (to acuminate when staminate), staminate ones persistent, pistillate ones caducous to persistent; bracteoles resembling bracts but smaller, pistillate ones in pairs at the base of the pedicel (absent when inflorescence single-flowered). Flowers actinomorphic, pedicellate; sepals free; petals and disc absent. Staminate flowers: pedicel with an abscission zone in the middle part; buds broadly ovoid, apiculate; sepals (2 or) 3 (or 4), ovate, valvate, apex acute, mucronulate; receptacle somewhat swollen; stamens 40-120 (in Malesia), filaments flattened, glabrous, anther dorsifixed, 4-celled, on both sides 2 cells above each other, opening introrsely and cruciately, connective often darker in colour, apiculate; pistillode absent. Pistillate flowers: pedicel with abscission zone (absent in C. spiciflorum), widening towards the apex; buds elongated; sepals 3-5, ovate to triangular, imbricate, base and central part thickened, margin entire, often hairy, apex acute, usually persistent; ovary 2-or 3-(or 4-)locular; 1 ovule per locule; style often very short to absent; stigmas deeply split, upper surface papillose. Fruits lobed capsules, opening septicidally and (sometimes incompletely) loculicidally, inner wall usually with shallow depressions; column with a broadened apex. Seeds subglobose, ± smooth, straw to brown when dry, usually mottled, testa not fleshy, caruncle absent.
Habitat & Ecology -In open to shaded places, evergreen to deciduous primary and secondary forests, often along rivers or streams; alluvial to dry soil; varying bedrock, but often on limestone. Altitude up to 1200 m. Flowering and fruiting: Thailand: January to March (fl), April to August (fr); Sumatra & Borneo: March to August (fl & fr); Java: August to December (fl & fr); Philippines: January to April (fl), April to September (fr).
Notes -1. The two epithets javanicum and spiciflorum have been inconsistently used for this species after Merrill (1917) interpreted the type of Acalypha spiciflora Burm.f. as belonging to it. This interpretation was based on the figure of Burmanʼs type in Flora Indica (Burman, 1768: 203). Later, in his annotation of the actual type in the Delessert Herbarium (G), Merrill identifies the type as a species of Claoxylon and not at all as Cleidion. Cleidion javanicum is thus the correct name for the species.
2. Part of continental Asian material is excluded here from C. javanicum and tentatively placed to the closely resembling species C. alongense Bennet & Subh.Chandra (type n.v.). This taxon is characterized by on average larger leaves with coarser teeth, densely hairy staminate rachises, 3-locular ovaries and 3-seeded fruits. It also seems to be mostly geographically apart from C. javanicum, occurring in mountainous areas at NE India, Nepal, Bhutan, China (Yunnan) and northern Burma. With this circumscription C. javanicum has almost exclusively 2-locular ovaries and 1-or 2-seeded fruits (only two specimens seen with perfect 3-seeded fruits).
Habitat & Ecology -Primary (to secondary) rain forests, often on ridges and hillsides, well to poorly drained soils. Altitude up to 900 m. Flowering and fruiting all year round.
Note -Cleidion salomonis, a species with large leaves, is synonymised with C. papuanum. The type of the former represents one end of a continuum in a vast variation in leaf and stipule size. The specimens with small or large leaves are also geographically intermixed.  Diagnostic characters -Only Malesian species with always clearly obovate leaves and gradually narrowing leaf base. and flowers not seen. Pistillate flowers not seen. Infructescences c. 12 cm long, basally 3-4 mm thick, with 3-8 fruits, 1 flower per node; bracts c. 5 mm wide, caducous to persistent; pedicels 4-9 cm long, with 3-6 bracteoles at basal part, abscission zone absent; sepals 5, ovate to obovate, 3-6 by 2.5-4 mm, apex rounded to obtuse; within the sepals remnants of a darker coloured seemingly disc-like structure surrounding the column and splitting into 1-2 mm long segments. Fruits: not seen completely, presumably 3-seeded, readily opening, ± smooth, dark brown to dark grey when dry, speckled. Seeds 17-19 by 17-19 mm; hilum 1-2 by 0.5-1 mm. Distribution -Philippines (Luzon). Notes -1. This species is known only from an incomplete type collection (including only leaves and remnants of infructescences and fruits). According to the original description (Quisumbing & Merrill, 1928), it is an up to 4 m high shrub occurring in damp forests along streams at low altitudes.

Cleidion ramosii
2. The absence of both staminate and pistillate flowers makes it impossible to indisputably confirm the placement of this species in genus Cleidion. The absence of extra-floral nectaries on both leaf surfaces, the presence of disc-like remnants inside the pistillate sepals, and the unusually long (relative to infructescence size) pistillate pedicels are deviating characters from all other (Malesian) Cleidion species.