Woody vine, occasionally described as a shrub or small tree; vegetative hairs medifixed; leaves opposite, sometimes biglandular at apex of petiole and usually bearing 1–3 pairs of small protuberant glands on margin near base, often on shallow toothlike extensions of margin. Inflorescence unbranched, terminating a leafy branch with full-sized leaves or lateral, axillary to a full-sized leaf and then usually bearing 1 pair of much-reduced leaves, these often deciduous; pedicels pedunculate; floriferous bracts and bracteoles eglandular, persistent. Sepals leaving outermost petal exposed in enlarging bud, the lateral 4 bearing 2 large glands, the anterior eglandular; glands peltate, raised on stout stalks that elongate to 0.7–1.5 mm during anthesis, borne below free part of sepals; corolla bilaterally symmetrical, the posterior petal differing from the lateral 4 in size, stance, and margin; petals abaxially thinly sericeous on claw and proximally on midrib of limb, adaxially glabrous; lateral petals lacerate on proximal half, distally subentire; posterior petal lacerate all around margin; androecium radially symmetrical; stamens with the filaments alike or longer opposite sepals than opposite petals, glabrous or abaxially sericeous distally, connate only at very base; anthers glabrous or rarely sparsely sericeous; pollen polyporate, without ectoapertures; gynoecium bilaterally symmetrical, the carpels 3; styles 3, the anterior longer than the posterior 2, weakly coherent in bud but soon separating during anthesis, slender, the large stigmas apical, elliptical-capitate and eccentric, dorsally elongated away from axis of flower. Fruit dry, breaking apart into 3 ellipsoidal mericarps (cocci) separating from an elongated pyramidal torus; coccus without wings or setae, bearing a rudimentary dorsal crest and otherwise completely smooth, the ventral areole elongate-elliptical. Chromosome number unknown.
One species, H. multiflora (Hook. & Arn.) Nied.; southern Brazil, Paraguay, and northeastern Argentina, in gallery forest or woodland, often near rivers. [map]
Molecular data [clade phylogeny] indicate that Heladena is sister to the Cuban endemic Henleophytum, which is initially surprising because the former has a smooth mericarp while that of the latter is setose. When one looks beyond that difference, the relationship is strongly supported by the stalked peltate calyx glands, hairy petals, weakly coherent but soon separating styles, and eccentric, elliptical-capitate stigmas.
Reference: Niedenzu (1928) recognized two sections in Heladena, "sect. Euheladena" [sect. Heladena] and sect. Hassleria Nied. [spelled Halleria in the original publication through a typographic error]. The only species of sect. Hassleria was Heladena hassleriana Nied., which is a synonym for Carolus chlorocarpus (Adr. Juss.) W. R. Anderson. Within sect. Heladena, Niedenzu recognized four species, following Jussieu (1840), but after careful study of the keys, descriptions, and specimens available, W. R. Anderson (unpublished data) found no consistent bases for recognizing more than one species in Heladena.
Etymology: The name Heladena comes from the Greek words for nail (helos) and gland (aden), and refers to the stalked peltate calyx glands. The spelling has been "corrected" by some authors to Heladenia, but the original spelling was Heladena and that must be retained.
Photos: H. multiflora
Drawing: H. multiflora