NEW SPECIES, NEW COMBINATIONS, AND NEW RECORDS IN CONVOLVULACEAE FOR THE FLORA OF THAILAND
I. TAXONOMIC & NOMENCLATURAL PROBLEMS
Four taxonomic and nomenclatural problems are discussed first to provide background for the scientific names used in the Flora of Thailand account.
A. The Argyreia splendens (Hornem.) Sweet problem
In herbaria the name Argyreia splendens has been applied to at least four distinct species, all of which share the common features of silvery sericeous leaf undersides and showy flowers of a purplish color. Beyond these generalities, however, botanists in various Asian countries have applied the name in divergent ways. We have been guilty of this as well and as it now turns out, the Chinese and Thai plants G.S. annotated over many years as A. splendens are not that species at all. In fact, the typification of the basionym for the name is complicated and it has been necessary to choose a neotype in order to stabilize its use.
As pointed out by Fang & Staples (1995: 318) Argyreia splendens has to be based on Convolvulus splendens Hornem. (1819) and not on Lettsomia splendens Roxb. (1824), as has long been established practice. Typification for Hornemann’s name, however, is complex. The protologue, published in a seed catalogue for a botanical garden in Denmark, states that a sterile plant (“Florentem non vidi”) cultivated in Copenhagen was the source for the brief description. Only a single sheet was located in C (Fig. 1) that is bona fide material from the historic Hornemann Herbarium. This sheet could be original material for Convolvulus splendens Hornem. On closer inspection, the sheet does not have the Hornemann name on it, it has no date or provenance linking it to the protologue, and it is labeled “Ipomoea splendens”, a name that was not published until 1824, five years after Hornemann’s publication of C. splendens. Furthermore, the specimen on the sheet—one detached leaf and one detached flower—does not match the protologue closely either. The flower is that of Ipomoea mauritiana Jacq. and because the protologue specifically says “Florentem non vidi” the flower has to be excluded as original material. The leaf, which is vaguely trilobed in shape, is glued on the sheet so that the underside is hidden; this makes it impossible to see if the leaf matches the protologue, which states: “foliis ovato-lanceolatis acuminatis subtus nervosis sericeis.” It is the final three words that are crucial: foliage of I. mauritiana is typically glabrous, whereas several Argyreia spp. have leaves that are silvery sericeous underneath. Also, leaves of Argyreia spp. are typically entire, never lobed, whereas leaves of I. mauritiana vary from entire to shallowly lobed to deeply digitately divided. On balance, what is visible of this leaf suggests that it came from a plant of I. mauritiana Jacq. and is not an Argyreia at all. Thus, the only specimen now extant in Copenhagen that belonged in Hornemann’s herbarium has to be excluded as original material for the name Convolvulus splendens Hornemann, and a neotype must be chosen to typify this name. The following nomenclatural summary does so.
Argyreia splendens (Hornem.) Sweet, Hort. Brit. Ed. 1. 289. 1826.— Convolvulus splendens Hornem., Hort. Bot. Hafn. suppl. 123. 1819. Type: India, Calcutta, cultivated in Hort. Bot. Calcutta, 8 Dec. 1814, [F. Buchanan-Hamilton sub] Wallich Cat. 1361.B (K-W, neotype, chosen here, barcode K000197075). Fig. 2.— Lettsomia splendens Roxb., Fl. Ind. 2: 75. 1824. Type: India, Calcutta, cultivated in Hort. Bot. Calcutta, [Roxburgh sub] Wallich Cat. 1361.1