9. Echinopepon Naudin, Ann. Sci. Nat., Bot., sér. 5. 6: 17. 1866.
Wild balsam apple [Greek echinos, hedgehog, and pepon, melon or pumpkin, alluding to prickly fruits] Wild balsam apple [Greek echinos, hedgehog, and pepon, melon or pumpkin, alluding to prickly fruits]
Plants annual [perennial], monoecious, climbing; stems <annual>, hairy [glabrous]; taprooted with branching secondary roots or roots slender-fibrous; tendrils [2–]3-branched. Leaves: blade reniform to orbiculate, deeply to shallowly palmately 3–5-lobed or dissected, rarely subentire, lobes deltate or ovate-triangular or rounded, margins entire or denticulate [dentate], surfaces
Species 19 (2 in the flora): sw United States, Mexico, Central America, South America.
<hispid to hispidulous>, eglandular. Inflorescences: staminate flowers 50–100 in branched or unbranched axillary racemes; pistillate flowers solitary, from same or different axils as staminate; <peduncles erect at apex>; bracts absent. Flowers: hypanthium campanulate; sepals 5(–6), linear to subulate or narrowly triangular [shallowly deltate, shallowly triangular, or widely ovate-deltate]; petals 5[–6], connate 1/4–2/3 length, white, triangular-ovate or oblong to deltate, [oblong-ovate to narrowly oblong], 3–6[–9] mm, glabrous or sparsely pubescent and eglandular or punctate-glandular to stipitate-glandular, corolla rotate or campanulate. Staminate flowers: stamens (4–)5; filaments inserted at base of corolla, connate into column; thecae <arcuate or recurved [sigmoid-replicate]>, connate, forming a head, not fused into ring, connective broadened; pistillodes absent. Pistillate flowers: ovary 2-locular, ovoid; ovules 2–5 per locule; style 1, <inserted at base of hypanthium>, columnar; stigma 1, a subglobose head; staminodes absent. Fruits capsular, tan to brown, obovoid [ovoid or cylindric], <symmetric>, beaked, dry, thin-walled, densely echinate, dehiscence through apical pores, beak sometimes caducous, calyptralike. Seeds 4–10, ovoid to quadranguloid beyond narrowed base, flattened, not arillate, margins not differentiated, surface corrugate to rugose or tuberculate. x = 12.
The monospecific Mexican genus Apatzingania was treated as distinct by R. McVaugh (2001b) and J. C. Rodríguez (1995) and included within Echinopepon as E. arachoidea (Dieterle) A. K. Monro & Stafford by A. K. Monro and P. J. Stafford (1998). It is distinct from other species of Echinopepon in its geocarpy and unilocular, single-seeded, indehiscent fruit. Monro and Stafford viewed these morphological features as adaptational consequences of geocarpy and noted that, on the basis of pollen morphology, seed ornamentation, and other features, E. arachoidea belongs in the species group that includes E. coulteri.
SELECTED REFERENCES Monro, A. K. and P. J. Stafford. 1998. A synopsis of the genus Echinopepon (Cucurbitaceae: Sicyeae), including three new taxa. Ann. Missouri Bot. Gard. 85: 257–272. Rodríguez, J. C. 1995. Distribución geográfica del género Echinopepon. Anales Inst. Biol. Univ. Nac. Autón. México, Bot. 66: 171–181.