Garcinia sect. Discostigma (Haask.) Hook. f.

Ngernsaengsaruay, Chatchai, Chanton, Pichet, Boonthasak, Weereesa & Bhuchaisri, Wanwisa, 2025, A taxonomic revision of Garcinia section Discostigma (Clusiaceae) in Thailand, PhytoKeys 261, pp. 275-315 : 275-315

Garcinia sect. Discostigma (Haask.) Hook. f. , Gen. Pl. [Benth. & Hook. f.] 1: 174 (1862); M. Gaudeul, P. W. Sweeney & Munzinger, PhytoKeys 239: 90. 2024.

≡ Discostigma Hassk. , Flora 25 (2, Beibl.): 33. 1842. Type. Discostigma rostratum Hassk. ≡ Garcinia rostrata (Hassk.) Miq.

Description.

Habit evergreen trees, dioecious; exudate yellow (in Garcinia minutiflora ), pale yellow (in G. santisukiana ), white, turning creamish white (in G. merguensis ) or creamish white (in G. rostrata ), sticky; branches decussate, horizontal or nearly horizontal; branchlets 4 - angular, glabrous. Terminal bud concealed between the bases of the uppermost pair of petioles. Leaves decussate; lamina coriaceous or subcoriaceous, glabrous; secondary veins curving towards the margin and connected in distinct loops and united into an intramarginal vein, with interrupted long wavy lines (glandular wavy lines, also called exudate-containing canals) of differing lengths; petiole grooved above, with a small basal appendage clasping the branchlet. Inflorescences terminal, axillary, or on branchlets at leafless nodes (in axils of fallen leaves), in fascicles (clusters) of 2–10 - flowered cymes, sometimes in a short thyrse of 5–12 flowers (in male inflorescences of G. minutiflora ), or a solitary flower (in female flowers of G. minutiflora and G. santisukiana ). Flowers unisexual, 4 - merous; bracteoles 2 or 4, triangular or semi-orbicular; sepals and petals decussate; sepals semi-orbicular, broadly ovate, ovate, suborbicular, or orbicular; petals broadly elliptic, elliptic, orbicular, suborbicular, or obovate. Male flowers: stamens numerous, united into 4 bundles, antepetalous (opposite the petals); anthers small, sessile to subsessile, 2 - thecous; pistillode mushroom-shaped (fungiform). Female flowers: staminodes present (in G. santisukiana ) or absent (in G. merguensis , G. rostrata ); pistil mushroom-shaped; ovary unlobed, bilocular, sometimes unilocular or four-locular (in G. yunnanensis ) ( Gaudeul et al. 2024); stigma sessile, unlobed, and smooth ( Gaudeul et al. 2024) or weakly to shallowly lobed and papillate. Fruits berries with a sticky yellow ( G. minutiflora , G. santisukiana ) or white, turning creamish white ( G. merguensis , G. rostrata ) exudate secreted from cut fruits, subglobose, globose, ovoid, or broadly ellipsoid, with a smooth surface and unlobed, with coriaceous pericarp; persistent stigma discoid and shallowly concave (in G. merguensis , G. rostrata ), flattened (in G. santisukiana ), or convex ( G. minutiflora ); persistent sepals small. Seeds 1–2, reddish brown, dark brown, black, or brown mottled with pale brown, depressed subglobose, depressed globose, or compressed, one side flat, another side slightly convex (elliptic or oblong in outline).

Garcinia sect. Discostigma is characterised by its terminal or axillary, or on branchlets at leafless nodes, cymose inflorescences in fascicles of 2–10 flowers, sometimes in a short thyrse of 5–12 flowers, or a solitary flower; flowers with 4 sepals and 4 petals; male flowers with numerous stamens united into 4 bundles and with sessile to subsessile, 2 - thecous anthers, with a pistillode; bilocular ovaries, sometimes unilocular or four-locular; weakly to shallowly lobed or unlobed and papillate or smooth stigmas; and fruits with a smooth surface and unlobed, with coriaceous pericarp, with a discoid persistent stigma, sometimes with a flattened or a convex persistent stigma, and with small persistent sepals. Distinguishing sectional morphological characters reported here were partly taken from Jones (1980) and Gaudeul et al. (2024).

According to Gaudeul et al. (2024), the unlobed and smooth stigmas are distinguishing sectional characters. However, from our examinations, all Thai species of Garcinia sect. Discostigma have weakly to shallowly lobed and papillate stigmas.

As stated by Gaudeul et al. (2024), the fruits of Garcinia sect. Discostigma are capped with a conspicuous discoid stigma. Furthermore, from the author’s observations, we found the persistent stigma in fruits of this section can be discoid and shallowly concave (in G. merguensis , G. rostrata ), flattened (in G. santisukiana ), or convex (in G. minutiflora ).

A section of 60 species worldwide ( Gaudeul et al. 2024), four species in Thailand [i. e., Garcinia merguensis Wight , G. minutiflora Ridl. , G. rostrata (Hassk.) Miq. , and G. santisukiana Ngerns. & Suddee )]. Numbers of species in Garcinia sect. Discostigma recognised by Jones (1980) and Gaudeul et al. (2024) is shown in Table 1 .