 |
| Panax siamensis J. Wen, in Wen, Krupnick et Esser, 2023. |
Abstract
We herein describe a new species, Panax siamensis J. Wen, from the tropical monsoon forests in northern Thailand. Panax siamensis is characterized by a combination of characters including horizontally elongated rhizomes with thick internodes, 3–5 whorled leaves each with 7–9 sessile and lanceolate leaflets, lanceolate bracteoles not persisting at the fruiting stage, 2-locular ovaries, and red fruits with a black top. The new species is most closely related to Panax zingiberensis C.Y. Wu & Feng from southeastern Yunnan province of China, sharing the character of sessile leaflets, but differing in that P. siamensis has well developed, elongated rhizomes (vs. compact, ginger-like rhizomes and rootstock in P. zingiberensis), and 7–9 leaflets (vs. (3–) 5–7 leaflets in P. zingiberensis). We also compare Panax siamensis to other related Asian Panax species, including P. assamicus Banerjee, P. bipinnatifidus Seem., P. pseudoginseng Wallich, and P. vietnamensis Ha & Grushv. The new taxon is preliminarily assessed as Vulnerable (VU D2), according to the IUCN Red List criteria. A taxonomic key is provided to facilitate the identification of P. siamensis and its close allies.
Key words: Araliaceae, conservation, ginseng genus, Panax, Panax siamensis J. Wen
 |
| Illustration of Panax siamensis J. Wen based on J. Wen 7371 (US) A habit B horizontal rhizome with base of stem C leaflet margin D leaflet abaxial surface E infructescence F enlarged infructescence G bracteoles subtending pedicels at flowering stage H older flowers after petals falling off, showing 2-locular ovary I young fruiting stage J seed K seed surface. |
 |
| Field images of Panax siamensis and its habitat A habitat in monsoon evergreen forest B infructescence showing red fruits with a black top C habit. Photo credit: A (Ricky Ward), B, C (Jun Wen). |
Panax siamensis J. Wen, sp. nov.
Diagnosis: Rhizomes horizontally elongated with thick internodes. Leaves 3—5 at the tip of stem, exstipulate, with 7–9 leaflets; leaflets sessile or nearly so, tapering toward the base, lanceolate, long acuminate at apex, long acute at base, serrulate to doubly so at margin, membranaceous, bristly along veins and veinlets on both surfaces. Ovary 2-locular. Fruits subglobose, bright red with a black top, persistent stigmas recurved, 1–2 seeded, 5–6 mm long, 7–8 mm wide, 3–3.5 mm thick. Seeds ovate, 5–5.5 mm long, 3–4 mm wide, 2.5–3.5 mm thick, surface rough.
Ecology: In shaded areas of monsoon evergreen hardwood forests, or in mixed evergreen hardwood and pine forests, granite bedrock.
Jun Wen, Gary Krupnick and Hans-Joachim Esser. 2023. Panax siamensis J. Wen, A New Species of the Ginseng Genus (Panax, Araliaceae) from northern Thailand. PhytoKeys. 234: 51-59. DOI: 10.3897/phytokeys.234.106289
