Echinopepon Naudin
Echinopepon Naudin, Ann. Sci. Nat. Bot. ser. 5. 6: 17. 1866.
Type: Echinopepon horridus Naudin, Bourgeau s.n. (P), Mexico, lectotype designated by Stocking, Madroño 13: 87. 1955.
Brandegea Cogn., Proc. Calif. Acad. Sci. ser. 2. 3: 58. 1890.
Vaseyanthus Cogn., Zoë 1: 368. 1891.
Apatzingania Dieterle, Brittonia 26: 131. 1974.

Annual or perennial climbers with up to 5 m long herbaceous shoots, fibrous roots or woody rootstock, and monoecius sex system. The leaves are simple, petiolate, with thin, angulate-cordate, often palmately 3-5(-9)-lobed or dissected blades, the margin entire or denticulate. The tendrils are simple or 2-3-fid. The flowers are small, the male inflorescence is a raceme or panicle, the female flowers are mostly solitary. The receptacle-tube is cup-shaped to urceolate or shallowly campanulate with five small or minute, green sepals. The corolla is rotate or campanulate with five ovate-triangular, white or cream-coloured petals, sometimes knobby-glandular (E. insularis). The filaments of the three to five stamens are fused into a central column, the anthers are all free, bithecous. The thecae are straight, curved or duplicate. The pollen is 5-14-colpate or colporate, some pantocolpate-inaperturate, sometimes the colpi with distinct margines, perforate (some weakly verrucate or micro-reticulate) medium-sized to large (polar axis 58-168 µm, equatorial axis 78-168 µm, (Khunwasi 1998)). The ovary is conic to ovoid, ± rostrate, with one or two placentae and 1-5 erect to ascending (rarely horizontal or pendent) ovules per locule. The style is short with fleshy, subglobose stigma. The fruit is ovoid or ellipsoid, operculate, glabrous or hairy, often conspicuously echinate, rostrate. In E. arachoidea the fruit is dry, subterranean (to 3.5 cm deep), on 6-9 cm long peduncle. The seeds are solitary or few, quadrangular or angular-ovoid, compressed with smooth, rugose or sculptured testa. The chromosome number is n = 12 (Ward and Spellenberg 1988).

The 22 species grow in forest-clearings, semi-deserts and ravines, on hillsides, roadsides, sand dunes and seaside gravel shores from the Southern United States to Northern Argentina. Some are weeds of cultivated ground.

Phylogenetically, Echinopepon is sister to a clade comprising Cyclanthera and Hanburia, from which it split about 15 million years ago (Schaefer et al., 2009; Schaefer & Renner 2011).