Inga unijuga Poepp. & Endl. Nov. Gen. & Sp. Pi. 3: 79. 1845.
Macrolobium limbatum Spruce ex Benth. Trans. Linn. Soc. 25: 307. 1865.
Vouapa limbata (Spruce ex Benth.) Taub. Bot. Centralbl. 47: 393. 1891.
Vuapa unijuga (Poepp. & Endl.) Kuntze, Rev. Gen. 1: 213. 1891.
Type Collection: E. Poeppig 2801, "Brasilia. In sylvis ad Ega," Nov. 1831- (HOLOTYPE W, isotypes P, W).
Vernacular Names: Brazil: "faveira."
This species, the two preceding ones, and the one following have been interpreted as comprising a complex which may have diverged from the M. campestre-M. arenarium line of relationship. However, this disposition is admittedly more a matter of convenience than of any very impressive morphology. Unquestionably, the nearest relative of M. unijugum is the following species, M. klugii. The leaflets of M. unijugum are quite different in shape and are borne on generally longer petioles, and its ovary is more or less pubescent. The typical variety has a somewhat different aspect, largely because the costa and primary veins are strongly impressed on the upper leaflet surface, while only the costa is impressed in the other varieties. Its shorter inflorescences, fasciculate in loose clusters, also lend a distinctive aspect to the typical form. These characters separate it from its nearest relative, variety mucronatum, but the latter also has mucronate bracteoles, longer anthers, and leaflets which are sometimes petiolulate.
Var. fanshawei is named in honor of Mr. D. B. Fanshawe, Conservator of Forests of British Guiana and outstanding student of the flora of this region. It is to be distinguished from the other varieties by its five, smaller sepals, which are somewhat dimorphic, and by its disjunct geographic distribution. Inga unijuga was described in 1845 on the basis of Poeppig 2801, although this number (nor any other number) was not cited in the original description. In 1870 Bentham described Macrolobium limbatum with a Spruce collection as the basis and it was not recognized that the two were synonymous until 1891 when Kuntze transferred the species to Vouapa as V. unijuga. There is no doubt that the two names apply to the same taxon after one has studied both collections. The Poeppig collection was very probably sterile. The initial description states that the portion relating to the legume was taken from field notes. Whereas the flowers of other species described by Poeppig and Endlicher at the same
time and in the same place were quite abundantly characterized, those of I. unijuga were described only as "Flores albi." It is probable that Poeppig only observed the flower color without obtaining flowering material. In fact, the label on the Paris sheet specifically states that he made the collection without flowers and fruit ("sine fl. et fr. legi").
Besides the sheet at Paris, which is identified only as "Inga?", there are two sheets at Vienna, one of which is annotated as "Inga unijuga Poepp." and is regarded as the holotype.