(3131) Proposal to reject the name <i>Kalanchoe guillauminii</i> ( <i>Crassulaceae</i> : <i>Cotyledonoideae</i> )

(3131) Kalanchoe guillauminii Raym.-Hamet in Bull. Mus. Natl. Hist. Nat., ser. 2, 20: 467. 20 Dec 1948 [Angiosp.: Crassul.], nom. utique rej. prop. Holotypus: cultivated at the Muséum national d'Histoire naturelle, Paris from material obtained by [J.-H.] Humbert (f. 353, 1933, no 17) from Mr [Frank Reginald] Long, director of the Port Elizabeth [now Gqeberha, Municipal] Gardens [Eastern Cape Province, South Africa], 1943 (P barcode P03350784). Kalanchoe rotundifolia (Haw.) Haw. (in Philos. Mag. J. 66: 31. 1825; based on Crassula rotundifolia Haw. in Philos. Mag. J. 64: 188. 1824) was the first species of this genus to be described from South Africa based on material collected in the Eastern Cape Province of the country (Figueiredo & Smith in Bradleya 35: 106–107. 2017). It is the species of Kalanchoe Adans. (Fam. Pl. 2: 248. 1763) with the most southwesterly natural geographical distribution range in southern Africa (Smith & al., Kalanchoe S. Africa: 213. 2019). With very little variation, the flowers of K. rotundifolia are small, narrowly and abruptly urceolate—a floral morphology referred to as “rotundifolioid”—with the corolla lobes being uniformly dull red to orange and the corolla tubes strongly greenish-infused, especially lower down, at the level of the calyx. The floral morphology of K. rotundifolia is also found in several related and unrelated species from southern Africa. The flowers are carried in few- and, generally, sparse-flowered corymbose cymes (Smith & Figueiredo in Haseltonia 23: 66. 2017). In contrast, the leaf morphology of the species is more variable, with leaf shape ranging from nearly round to oblong-elliptic to elliptic-obovate (Smith & Figueiredo in Phytotaxa 603: 285. 2023; Smith & Crouch in Phytotaxa 659: 271. 2024). Jean-Henri Humbert (1887–1967) was an extraordinarily prolific collector of botanical specimens for deposition in herbaria, and during a long career as botanist and institutional leader he amassed more than 50,000 such specimens during several collecting trips (Gunn & Codd, Bot. Explor. S. Africa: 194. 1981; Dorr, Pl. Coll. Madagascar Comoro Isl.: 214–218. 1997; Figueiredo & Smith in Regnum Veg. 161: 149–151. 2024). Humbert is known to have collected in South Africa from “Aug. 1933 into early 1934” (Gunn & Codd, l.c.). During this visit to the country he inter alia visited Gqeberha (then known as Port Elizabeth) and there met with Mr Frank Reginald Long (1884–1961), who was the Director of the city's municipal gardens. Long is known to have had more than a passing interest in succulents, and material of a kalanchoe that he had in cultivation in Gqeberha was given to Humbert. Humbert in turn passed the material for cultivation to André [Louis Joseph Edmond Armand] Guillaumin (1885–1974), who, like Humbert at the time, was also attached to the Muséum national d'Histoire naturelle, Paris, France, where Guillaumin was the Head of Horticulture and later Deputy Director, until his retirement in 1956. Raymond-Hamet (1890–1972), the undisputed global expert on Kalanchoe during the 20th century (Smith in Bradleya 38: 122. 2020), was alerted to the material obtained from Long by Humbert and stated (Raymond-Hamet in Bull. Mus. Hist. Nat. (Paris) sér. 2, 20: 465. 1948, translated from the original French): “I owe it to the kindness of Professor Guillaumin for having been able to study a flowering sample of this [Humbert's] Kalanchoe in the flesh [i.e., living material], and to the kindness of Professor Humbert for having been able to examine in the dry [preserved] state the first specimen of this same Kalanchoe to flower at the Museum. To both of them I am happy to express my sincere thanks.” Raymond-Hamet (l.c.: 467) published the name K. guillauminii for this material. Notably, the Kalanchoe material that Humbert obtained from Long in Gqeberha was not recorded as having been collected from Gqeberha, nor, for that matter, from the Eastern Cape. Long therefore could well have obtained it from elsewhere in eastern southern Africa where several kalanchoes occur naturally, before placing it in cultivation in Gqeberha and passing it to Humbert. The only preserved specimen, as far as could be determined, of the name Kalanchoe guillauminii was cited by Raymond-Hamet (l.c.: 465) in the protologue and is labelled “Afrique du Sud: Mr. Humbert f. 353/1933 no 17 | environs? de Port Elizabeth | Hort. Bot. Pariensis anno 1943” (P barcode P03350784). It is here interpreted as the holotype of the name. However, the specimen consists of a single, early (or late?) inflorescence only, along with a folded paper capsule that might contain additional reproductive or vegetative fragments. Regardless, from the dried inflorescence attached to the type sheet it is evident that the sepals could be substantial and at least half as long as the corolla tube, despite Raymond-Hamet's (l.c.: 466) descriptive text stating that the sepals are 1.75 mm long. As recently shown by Rodewald & al. (in Ann. Bot. (Oxford) 135: 1318. 2025), those southern African Kalanchoe species, especially K. alticola Compton (in S. African J. Bot. 41: 47. 1975) and K. waterbergensis van Jaarsv. (in Bradleya 35: 169. 2017), with largely “rotundifolioid” flowers but substantial sepals are not closely related to K. rotundifolia, despite their overall flower morphologies being remarkably similar. It is therefore possible that Kalanchoe guillauminii could be the earliest name published for the southern African species that is today consistently known as K. alticola, or the name K. guillauminii could even be interpreted as applying to a different species with a well-entrenched name. The name Kalanchoe alticola has been adopted in the Flora of Southern Africa treatment of Kalanchoe (Tölken in Leistner, Fl. S. Africa 14: 63, 65. 1985), in the most recent global-level synopsis of the genus (Descoings in Eggli, Ill. Handb. Succ. Pl. Crassulaceae: 145. 2003), as well as in the most recent treatment of southern African kalanchoes (Smith & al., l.c.: 138), and is in use in both online (https://opus.sanbi.org/items/fc8fbd6d-52b0-4342-b78d-49ff1a7c0d46) and printed (Germishuizen & al. in SABONET Rep. Ser. 41: 364. 2006) catalogues of the flora of South Africa, and online (https://africanplantdatabase.ch/en/nomen/specie/55032/kalanchoe-alticola-compton) and printed (Klopper & al. in SABONET Rep. Ser. 42: 249. 2006) catalogues of the flora of continental Africa. The name Kalanchoe guillauminii has been synonymised under K. rotundifolia for more than 40 years and rejecting it will have no negative nomenclatural effect. Therefore, to avoid a disadvantageous name change and future redundant nomenclatural discussions, the rejection of the name K. guillauminii is proposed in accordance with ICN Art. 56 (Turland & al. in Regnum Veg. 162. 2025). Dr John Wiersema, Smithsonian Institution, Washington, D.C., U.S.A., and Dr Melanie Schori, United States Department of Agriculture, National Germplasm Resources Laboratory, Beltsville, Maryland, U.S.A., are thanked for their meticulous editing of the proposal.