NEW SPECIES, NEW COMBINATIONS, AND NEW RECORDS IN CONVOLVULACEAE FOR THE FLORA OF THAILAND
(K-W, lectotype, chosen here, barcode K000197074).— Ipomoea splendens (Roxb.) Sims,
Bot. Mag. 53: tab. 2628. 1826. Fig. 3.
The two specimens above are both the same species and may have originated from the same plant in the Calcutta Botanic Garden. Sheet 1361.1 bears an annotation in the bottom right corner “Convolvulus (Lettsomia) splendens Roxb HBC” that may be in Roxburgh’s own hand; this specimen is the best choice as lectotype for L. splendens Roxb. The sheet labeled 1361.B has a handwritten ticket at top left in Francis Buchanan-Hamilton’s handwriting that dates it in 1814; this sheet is old enough to pre-date the Hornemann name and is chosen as neotype for C. splendens. Hornemann’s protologue notes that the plant grown in Copenhagen was introduced there in 1818 and the habitat is “in Ind. orient. ad Chittagong”—identical with Roxburgh’s entry from both Hortus Bengalensis (Roxburgh 1814) and Flora Indica (Roxburgh 1824), which raises the possibility that Roxburgh, or his successor and literary editor, Wallich, sent seeds to Hornemann from the plant growing in the Calcutta Botanic Garden. The Buchanan-Hamilton specimen at 1361.B predates Hornemann’s acquisition of the seeds from Calcutta and may well have been made from the same plant that provided that seed.
As will be immediately clear from Fig. 2 and 3, the true A. splendens has a distinctive aspect that is evident from herbarium sheets: ovate-lanceolate leaves, dark green above and silvery hairy below; long peduncles (several times longer than the subtending leaf petiole) bearing crowded, even capitate, cymose clusters of showy flowers; sepals that are equal in length, broadly elliptic to subcircular in shape, and densely silvery hairy on the backs; funnelform, dark colored corollas with a vaguely 5-lobed limb. This plant, originating from Bangladesh, looks nothing like what has been called A. splendens in SE Asia and tropical China. Unfortunately, we have long misinterpreted Argyreia splendens and many specimens we have annotated as such are all wrongly named. The Thai plants, in part, agree more closely with A. laotica Gagnep., and in part, with a narrowed concept for A. mollis, discussed next. It will be necessary to re-examine the Chinese material to evaluate its correct taxonomic status and the name for it.
B. The re-separation of Argyreia mollis (Burm.f.) Choisy and A. obtecta (Choisy) C.B.Clarke
Van Ooststroom (1943) and Van Ooststroom & Hoogland (1953) applied Argyreia mollis in a broad sense that encompassed plants from Burma to China and southward through Thailand and Malesia as far as Bali. Van Ooststroom included as synonyms A. obtecta (Choisy) C.B.Clarke, among others. Study by the second author in her M. Sc. dissertation disclosed that Thai plants can readily be separated into two entities based on a variety of morphological characters. The first author has compared these to type specimens for several of the names synonymized by Van Ooststroom and found that these two entities correspond to A. obtecta and A. mollis in a narrowed sense (e.g., Staples & Jacquemoud 2005). The following table enumerates the characters useful for distinguishing these two from A. laotica and genuine A. splendens, which does not appear to occur in the Flora of Thailand area (see A above).