Woody vine, occasionally described as shrubby; stipules absent or represented by minute rudiments borne on petiole just above base; leaves decussate; petiole eglandular or, more commonly, bearing 2–8 small glands in 2 rows; lamina bearing small glands on margin, occasionally only a few near base but usually several to many extending distally 3/4 or more of the distance to apex. Inflorescences paniculate, lateral and terminal, often decompound, with the flowers borne in short mostly decussate pseudoracemes, these sometimes condensed to form umbels or tight corymbs of 4 or 6 flowers; floriferous peduncle mostly absent, occasionally developed, short; bracteoles eglandular, borne near middle of peduncle when peduncle is developed. Flowers radially symmetrical in all their whorls; sepals valvate, completely concealing petals during enlargement of bud, weakly connate most of their length, revolute in anthesis but separating incompletely and irregularly, abaxially sericeous, adaxially glabrous, all eglandular; petals white, spatulate, glabrous or abaxially very sparsely sericeous; stamens 10, glabrous; filaments connate only at very base, straight, those opposite petals slightly longer than those opposite sepals; anthers alike; receptacle glabrous between androecium and gynoecium; gynoecium comprising 3 carpels connate in the ovary; styles 3, inflexed distally, equal, slender but terete, truncate at apex with the stigma terminal. Fruit dry, usually with only 1 samara developing, indehiscent (? see discussion below); samara orbicular or transversely elliptical, the lateral wings membranous with many looping anastomoses, cleft to nut at apex, continuous at base, the margin entire or undulate; dorsal wing free from lateral wing at base, extended forward at apex through gap in lateral wing; intermediate winglets none. Chromosome number unknown.
One variable species, Flabellaria paniculata Cav., widely distributed in equatorial Africa in thickets, woodlands, and forests, especially along rivers. [map] — Regional key to genera: Kenya & Tanzania. — See account of Flabellariopsis for a key separating it from Flabellaria.
Niedenzu (1928, p. 39) showed the ovary in Flabellaria with one locule fertile and the other two empty, but all the ovaries dissected by W. R. Anderson had all three locules equally fertile. Nevertheless, usually only one of the carpels develops into a samara, and none of the specimens seen showed the samara separating from the flower, suggesting that in this genus the fruit may be indehiscent, the single samara falling from the plant with the remains of the flower and the pedicel.
DNA sequences (Davis & Anderson, 2010 [pdf]) place this genus with very strong support as sister to the Amazonian genus Malpighiodes. That relationship is reflected in several aspects of their morphology: valvate sepals concealing the petals in the developing bud, truncate styles with terminal stigmas, and essentially identical samaras. Malpighiodes differs in having its lamina glands in the abaxial surface, the sepals all biglandular, the corolla yellow and bilaterally symmetrical, and the filaments connate for approximately half their length.
Flabellaria is unique in the family in having the sepals not only valvate in the bud, but at least weakly connate. Inspection of open flowers always shows some pairs of sepals still connate for part of their length.
References: Flabellaria was treated by Niedenzu (1928) and more recently in various African floras, such as "Flora of West Tropical Africa," by J. Hutchinson & J. M. Dalziel, second edition revised by R. W. J. Keay, vol. 1(2), p. 353. 1958 [pdf].
Uses: Burkill (1997) gives several folk remedies based on or incorporating parts of Flabellaria paniculata, but he adds, "Chemical analysis has not detected any active principle to the plant . . . .".
Photos: F. paniculata
Drawing: F. paniculata