Appunia Hooker f. in Benth. & Hook, f., Gen. Pl. 2: 120. 1873.
Bellynkxia Mull.-Arg., Flora 48: 465. 1875.
Type. Morinda roioc L.
In Mem. N. Y. Bot. Gard. 17: 354-360. 1967, I reviewed the species of Appunia (with the exception of A. seibertii Standi.) and concluded that the genus could not be separated from Bellynkxia Müll. Arg. It now is evident, after an investigation of the genus Morinda L., that Appunia, likewise, must be considered synonymous with Morinda.
The main distinction between Appunia and Morinda lies in the degree of connation of the ovaries. In Appunia the ovaries of the individual flowers are free and the style is not branched, ending in a club-shaped, rounded stigma, whereas in Morinda the ovaries of the individual flowers are partly connate at the base and the style is 2-branched. The fruit in Morinda is a fleshy compound berry, whereas in Appunia the fruit consists of one to several distinct and fleshy pyrenes.
Among the neotropical species of Appunia and Morinda, at least two, i e, Appunia triphylla Ducke and Morinda hoffmannioides Standi., show either an intergradation in characters or a tendency towards the delimiting characteristics of the other genus. Appunia triphylla has a 2-branched style, as in Morinda and sessile inflorescences as are often found in M. royoc L. Morinda hoffmannioides has 2-branched styles, but the 5-6-flowered inflorescences have flowers with their calyces free above the basal third, while the young fruits are coherent only in the basal third, approaching the free condition found in Appunia. When Standley described this species, he expressed doubt (Field Mus. Publ. Bot. 22: 193-194. 1940) that this taxon actually belonged in Morinda, since he observed that the few fruits in a head were “coherent only at the base.” Inasmuch as the calyces and fruits are nearly free in Morinda hoffmannioides, thus approaching the condition in Appunia, and since Appunia triphylla has 2-branched styles as in Morinda, it would appear that in these two species, at least, there is an overlapping or tendency toward the overlapping of generic characters. A more natural consideration would seem to regard such variation as consistent within one genus, diverging subgenerically into the two previously recognized generic categories of Appunia (including Bellynkxia) on the one hand, Morinda on the other. Accordingly, the following new combinations under Morinda are necessary.