Elephantomene Barneby & Krukoff, 1974

Sousa, Julio Dos Santos De & Gurgel, Ely Simone Cajueiro, 2023, Emended description of the South American genus Elephantomene (Menispermaceae), Phytotaxa 579 (1), pp. 32-38 : 33

Elephantomene Barneby & Krukoff , Lloydia 37(1): 28–29. 1974. Fig. 1–3

Cionomene Krukoff, Phytologia 41: 241.1979

Liana 6–35 cm diâm.; rhytidome ivory, fissured. Leaves alternate, basifixed; venation suprabasal actinodromous; primary veins 5, plinerved, convex on the abaxial surface; adaxial surface glabrous, abaxial surface tomentose or velutinous. Petiole semi-cylindrical; basal pulvinus conspicuously swollen; apical pulvinus inconspicuous. Bracts of the inflorescence ovate, velutinous. Inflorescences in simple racemes or panicles, multiflorous or pauciflorous, axillary or supra-axillary. Flowers unisexual, pediceled, actinomorphic, dichlamydeous. Staminate flowers with isostemonous androecium; sepals 6, biseriate; 6 petals and 6 free stamens elevated in a central column; anthers longitudinally dehiscent. Pistillate flower hypogynous; sepals 6, biseriate; petals 6; staminodes 6; carpels 3; one ovule degenerated and one developed per carpel; stigma apical. Drupes raised by a tripartite gynophores; stigma scar subbasal; epicarp subligneous; mesocarp fleshy; endocarp in the shape of an inverted “U,” woody, the outer surface is ornamented with a characteristic pattern of two inverted “U” shaped grooves, following the long curvature and connected by a network of lesser, horizontal veinlets; seed with endosperm ruminate, in the shape of an inverted “U,” with external tegumentary membrane; condyle septiform, vertical to the longitudinal axis of the seed; embryo curved in the mid region.

Elephantomene is a neotropical genus, with distribution in South America: Brazil, Ecuador, French Guiana and Peru ( CRIA 2022, Sousa 2016, Tropicos 2022). This genus is monospecific and easily identified by the presence of a tripartite gynophores in the pistillate condition and by stamens elevated in a central column in the staminate condition.

Type: Elephantomene eburnea Barneby & Krukoff

Figures

FIGURE 1. Elephantomene eburnea Barneby & Krukoff. A. Branch with pistillate inflorescences. B. External whorl of the staminate flower. C. Internal whorl of the staminate flower, showing the sepals, petals and stamens fixed on a column. D. Outer sepal. E. Petal surrounding the stamen. F. Petal. G. Stamen. H. External whorl of the pistillate flower. I. Internal whorl of the pistillate flower, showing the sepals, petals, gynoecium and staminodes. J. Petals, gynoecium, staminodes and stigma. K. Petal and staminode. L. Carpel. M. Detail of an infructescence with a drupe or attached to one of the three gynophores. N. External structure of the endocarp. O. Internal structure of the endocarp in the shape of an inverted “U”. P. Endosperm ruminate. A, H–L Ortíz 237 (INPA, MO), B–G Prance et al. 24137 (NY) and M–P Ortíz 237 (INPA, MO). Drawing by Carlo Alvarez and Julio Sousa.

FIGURE 2. Elephantomene eburnea Barneby & Krukoff. A. Adaxial leaf surface. B. Abaxial leaf surface. C. Bracts. D. Pistillate flower. E. Inner sepal. F. Outer sepal. G. Petal and staminode. H. Gynoecium surrounded by petals and staminodes. I. Carpels with stigmas.

FIGURE 3. Floral diagram of Elephantomene eburnea Barneby & Krukoff. A. Staminate flower. B. Pistillate flower.