Type:— Wissadula zeylanica Medic. (1760:24) = Wissadula periplocifolia (L.) Presl. ex Thwaites.

Subshrubs or shrubs, creeping or erect, or treelets. Trichomes in vegetative and sexual parts, whitish, hyaline or ferruginous, simple, glandular or not, fasciculate, fasciculate-stipitate, multiradiate, or multiradiate-stipitate. Branches terete, erect, rarely patent (W. excelsior). Stipules in pairs, rarely epipetiolar (W. glechomifolia), filiform, linear, lanceolate or elliptic, deciduous or persistent, pubescent. Leaves petiolate, petiole terete (sometimes subsessile), simple, alternate, with entire margins (rarely lobed, with acute lobes); blade usually upper surface green and lower surface pale green, sometimes concolor, rarely conspicously upper surface dark green and lower surface pale green (W. stipulata and W. cuspidata), membranous or chartaceous (sometimes transparent when dry), variable in shape (from orbicular to lanceolate and deltoid) and base type (cordate, sometimes with imbricate lobes, subcordate, truncate, rounded or attenuate), apex type (acute, acuminate, cuspidate or obtuse, rarely apiculate or mucronulate) and margins (entire, undulate, serrate or crenate, rarely revolute, frequently ciliate, with trichomes simple); adaxial surface glabrous to pubescent; abaxial surface publescent with trichomes fasciculate, multiradiate or multiradiate-stipitate; venation broquidodromous. Synflorescences frondose-bracteate, pedunculate, pyramidal, rarely oblong, lax or congested, sometimes with uniflorous branches (W. caribaea); coflorescences in compound-racemes; accessory branches with 2(–3) flowers; anthopodium thin during flowering, thick during the fruiting stage; bracts leaves-like, decreasing gradually in size toward the stem apices. Flowers pentamerous, pedicellate; calyx gamosepalous, campanulate, sometimes accrescent during the fruit stage; sepals acute, cleft up to the median or lower region of the calyx; abaxial surface pubescent, with trichomes hyaline or ferrugineous; adaxial surface frequently whitish, pubescent; corolla white (sometimes with a yellow), beige, yellow, rarely beige to pink (sometimes purple in the middle); petals spathulate, with margin pubescent at the base (fasciculate-stipitate trichomes); staminal column about 1 mm long, with few trichomes, hyaline, simple and fasciculate-stipitate; free portion of the filaments three times longer than the column; anthers yellow, oblong; ovary superior, with 3–7 free carpels, (1–2–)3 ovules per loculus; styles slightly longer than filaments; stigma capitate. Schizocarp with 3–6(–7) mericarps, awned (rarely muticous), partially dehiscent, with constriction conspicuous or inconspicuous, glabrous, puberulous or pubescent, sometimes only on the fusion of the carpels and on the upper portion of the mericarps (trichomes simple, glandular or fasciculate, rarely multiradiate); seeds usually 3 (rare 1 in W. stipulata), 2 collateral and globose upper seeds, and 1 subovate lower seed, glabrous or pilose, with trichomes simple; hilum region pilose (sometimes glabrous), with trichomes simple, long, rarely short.

Note — Medicus (1787) described Wissadula while describing W. zeylanica [superfluous name], mainly based on the fruit morphology of a plant collected in Ceylon by P. Hermann in the early 1670s. Based on the number of ovules per loculus and the morphology of the mericarp, Schumann (1891) later recognized three sections for the genus: Wissada (one ovule), Wissadula (two or three ovules), and Wissadulastrum (with “endoglossum”; mericarps horizontally divided). Fries (1908) accepted the sections Wissada and Wissadula and recognized a new genus, Pseudabutilon, for species included in the section Wissadulastrum. Grisebach (1864) transferred the taxa of the section Wissada to the genus Sida L., highlighting their similarity with Wissadula and the need for further studies in the genus Wissadula.

The section Wissada is currently represented by three species: W. divergens (Benth.) Benth. & Hook.f. (endemic to Ecuador), W. fadyenii R.E.Fr. (from the Antilles to Bolivia), and W. stipulata Bovini (endemic to the State of Mato Grosso do Sul in Brazil); the section Wissadula comprises the remaining 29 species of the genus. The Wissadula species can be found in all habitats, especially in disturbed and dry areas on forest edges or clearings, and may form large populations or be represented by only one individual.