Paralasianthus H. Zhu, 2015

Zhu, Hua, 2015, Paralasianthus (Rubiaceae), a new genus from Southeast Asia, Phytotaxa 202 (4), pp. 273-278 : 274

Paralasianthus H. Zhu , gen. nov.

Type: — Paralasianthus dichotomus ( Korthals 1851: 224) H. Zhu (Basionym: Mephitidia dichotoma Korthals ).

Dysosmia ( Korthals 1851: 224) Miquel (1859: 325) . Mephitidia subgen. Dysosmia Korthals (1851: 224) , non Roemer (1846) Type: — Dysosmia dichotoma (Korthals) Miquel (1859: 326) [= Paralasianthus dichotomus (Korthals) H. Zhu ]

Proximus Saprosmo sed setis stipularum et bractearum inconspicuis vel minutis, venationibus brachidodromis, petilolis non-articulatis differt. Simile Lasiantho, sed ovariis bilocularis, pyrenis 2, pariete pyrenae tenui differt. A Amaracarpo simile sed plantis glabris, stipulis minutis, bracteis et bracteolis inconspicuis, cymis axillaribus vel sub axillaribus differt.

Shrubs or treelets, glabrous, 2–3 m tall; branchlets terete or compressed in the youngest internodes, or incrassate at nodes. Stipules usually very small, subulate or triangular, usually 1–3 mm long; with small colleters present on the inside at the base. Leaves petiolate; blades elliptic-oblong to lanceolate, chartaceous to coriaceous, the base acute, cuneate or subround, the apex cuspidate to caudate or mucronate; midribs and veins prominent beneath or on both surfaces; secondary veins joined near the leaf margin and forming a looped venation; tertiary venation reticulate or subparallel. Inflorescences subaxillary, cymose, pedunculate or sessile; bracts and bracteoles small, subulate. Flowers pedicelate or sessile.Calyx usually obconical, with 4–5 minute teeth; corolla tubular, glabrous outside, pubescent the upper half of throat, the lobes 4–5, pubescent inside; anthers 4–5; ovary 2(–3)-locular, with one ovule per locule. Drupes compressed, ovoid, 2(–3)-pyrenate; pyrenes wall thin or thick on adaxial side.

Distribution —Five species are recognised in this genus, ranging throughout tropical South East Asia, with one species widely distributed in South East Asia, one in western Malesia, and the other three endemic to the Philippines, Thailand and the Hainan Province of China.

Notes:—This genus differs from Saprosma in the lack of conspicuous colleters on the inside of the base of the stipules and bracts (except very minute ones), petioles without articulation, and leaves with looped venation. It differs from Amaracarpus by being glabrous plants, with axillary or subaxillary cymes, stipules subulate or triangular, free, entire bracteoles, not forming a compact structure with stipules and reduced leaves. It differs from Lasianthus in usually having a 2-locular ovary and drupes with 2 thin-walled pyrenes. Its unique combination of characters, i.e. glabrous plants with very small stipules, looped leaf venation, usually 2-locular ovary and 2-pyrenate drupes, clearly separates it from Lasianthus , Saprosma and Amaracarpus .

The systematic position of this new genus remains uncertain. Morphologically is positioned between Saprosma and Lasianthus . However, Saprosma was placed in the tribe Paederiae by Puff (1992) based on morphological characters, while Lasianthus was referred to the new tribe Lasiantheae by Bremer & Manen (2000), based on molecular evidence.