Derris tonkinensis Gagnepain (1913: 349)

Song, Zhu-Qiu, Li, Shi-Jin, Vu, Quang Nam & Khang, Nguyen Sinh, 2022, Taxonomic notes on the genus Millettia (Fabaceae: Millettieae) in Vietnam, Phytotaxa 571 (2), pp. 169-185 : 179-181

2. Derris tonkinensis Gagnepain (1913: 349) .

Type: — VIETNAM. Tonkin , baie d’Along, 3 July 1885, B. Balansa 1189 (lectotype: P00700373 image!, designated by Lôc & Vidal 2001: 78; isolectotypes: P00700374 image!) .

= Millettia boniana Gagnepain (1913: 351) . Type: — VIETNAM. Tonkin, prov. Ha Nam, Vo Xa , 12 September 1891, H. F. Bon 4871 (lectotype designated here: P02141778 image!; isolectotypes: P02141779 image!, P02141780 image!, P00800923 image!), syn. nov.

Millettia boniana was described by Gagnepain (1913: 351) as a new species based on a single flowering collection from Tonkin, Vietnam (H. F. Bon 4871, Fig. 5 : A). This is a poorly known species. The species is known only from the type locality, and its fruit information is still not provided in any literature. Lôc & Vidal (2001) stated that this species was also found in one locality in Thailand, but did not provide any voucher information. In Flora of Thailand, Mattapha (2020) recorded 27 species of Millettia , but did not include this species. We did not find any other specimens of the species except for four sheets of type specimens from Vietnam. In the protologue, Gagnepain (1913) described the species with terminal and axillary inflorescences, although he was not sure about its growth habit (“Arbor vel frutex scandens?”). Both Millettia and Derris Loureiro (1790: 432) contain trees and climbers, but Millettia species usually bear axillary inflorecences ( Song et al. 2021), while many species of Derris are often recorded with terminal inflorecences ( Chen & Pedley 2010, Sirichamorn et al. 2012). Millettia boniana was also described with slender branches bearing whitish lenticels, estipellate leaflets, whitish flowers, glabrous petals, a standard petal without basal callosities and auricles, biauriculate wings, and fewer ovules per ovary ( Gagnepain 1913). In these characters, M. boniana is also very similar to some species of the genus Derris such as D. tonkinensis .

Specially, in the discussions of Millettia boniana, Gagnepain (1913) pointed out that the collector (H. F. Bon) of its type specimens wrote Derris on the label. Furthermore, we found that a flowering syntype of Derris tonkinensis , collected by H. F. Bon (3347, Fig. 5C ) from Tonkin, Vietnam, is strikingly similar to the type specimens of M. boniana in morphology. In addition, a fruiting specimen that was collected by H. F. Bon (3381, Fig. 5D ) is consistent with M. boniana in appearance, but it has indehiscent, thin and winged pods and belongs to D. tonkinensis . Millettia and Derris are very similar in morphological characters, especially when lacking fruiting material, and this has caused transfer of some species names between the two genera ( Merrill 1910, How 1954, Song et al. 2017a, Song & Pan 2022). In fact, the lectotype (B. Balansa 1189, Fig. 5B ) and isolectotypes of D. tonkinensis were recorded by Drake (1891: 188) as Millettia sp. Based on these analyses, M. boniana is proposed here as a new synonym of D. tonkinensis .

In addition, in the protologue of M. boniana Gagnepain (1913) just cited Bon 4871, but did not specify the holotype. Lôc & Vidal (2001) provided the type information of M. boniana [“Type: Bon 4871, Viȇtnam, Nam Ha, Vo Xa, sept. 1891, fl. (holo-, P!; iso-, P!)”], which means presence of more than one duplicates of this gathering and all of them should be considered as syntypes (see Art. 7.11 Ex. 12 and Art. 40 Ex. 3, Turland et al. 2018). We traced four duplicates of this collection in P, of which three labelled “TYPE” and the fourth labelled “ISOTYPE”. We designate one of them (P00700373) with “TYPE” as the lectotype of M. boniana .

Figures

FIGURE 5. Derris tonkinensis Gagnep. A. lectotype of Millettia boniana Gagnep. (H. F. Bon 4871, P02141778, https://science.mnhn. fr/institution/mnhn/collection/p/item/p02141778); B. lectotype of D. tonkinensis Gagnep. (B. Balansa 1189, P00700373, https://science. mnhn.fr/institution/mnhn/collection/p/item/p00700373); C. flowering syntype of D. tonkinensis Gagnep. (H. F. Bon 3347, P02927191, https://science.mnhn.fr/institution/mnhn/collection/p/item/p02927191); D. fruiting specimen of D. tonkinensis Gagnep. (H. F. Bon 3381, P02927188, https://science.mnhn.fr/institution/mnhn/collection/p/item/p02927188). ©Copyright of Muséum national d’Histoire naturelle.