6. Cyclanthera Schrader, Index Seminum (Göttingen). 1831: 2. 1831.
Bur cucumber [Greek kyklos, circle, and antheros, blooming, alluding to single, ringlike stamen] Bur cucumber [Greek kyklos, circle, and antheros, blooming, alluding to single, ringlike stamen]
Cremastopus Paul G. Wilson
Plants annual, monoecious [dioecious], climbing; stems <annual>, glabrous or hairy; roots fibrous; tendrils unbranched or 2[–3]-branched, <branches unequal in length>. Leaves simple or compound; blade lanceolate to orbiculate, [unlobed or shallowly 3–9-lobed to palmately 3–5-lobed] 3–7-foliolate (3–7-palmatisect), <[divisions narrowly broadly lanceolate to elliptic-lanceolate or oblanceolate to obspatulate] base attenuate to cordate>, margins coarsely serrate to shallowly or deeply lobed [to serrulate or denticulate], abaxial surface glabrous, adaxial surface scabrous with hair bases. Inflorescences: staminate flowers in axillary racemes or narrow panicles with or without well-differentiated main axis; pistillate flowers solitary, usually from same axils as staminate, <peduncles erect at apex>; floral bracts <caducous>, filiform. Flowers: hypanthium campanulate to shallowly cupulate; sepals vestigial [5, ovate-triangular to triangular]; petals 5, connate 1/3[–2/3] length, white [greenish or yellowish], oblong-ovate to triangular, 1–1.5[–5] mm, glabrous, <minutely papillate-glandular adaxially>, corolla rotate [campanulate]. Staminate flowers: stamens 5; filaments inserted at receptacle base, connate into central column, <0.2–2 mm (anthers sessile or subsessile to short-columnar)>; thecae connate-fused into continuous, horizontal ring as a single structure (synanther), forming a head, <dehiscing by continuous slit>, connective broad; pistillodes absent. Pistillate flowers: ovary usually 1-locular, ovoid to elliptic-ovoid or subglobose; ovules (1–)2–6 per locule; style 1, short-columnar; stigma 1, depressed-subglobose; staminodes absent. Fruits fleshy-capsular, green to light green, narrowly obliquely ovoid to obliquely globose or obovoid (or subglobose to broadly ellipsoid), gibbous, acute to obtuse at both ends, densely echinate [to smooth or very sparsely echinate], irregularly and explosively dehiscent. Seeds (1–)4–12, ovoid to oblong, compressed, not arillate, margins not winged but sculptured, surface [smooth, roughened, muriculate, or] tuberculate. x = 16.
Species of Cyclanthera are characterized by their annual duration, relatively small flowers, androecium of a single, horizontal, continuous, circular theca, and gibbous, echinate, placental arm. Nectaries are derived from secretory hairs on the hypanthium (S. Vogel 1981). The northern Mexican Cremastopus was distinguished by the production of a single ovule, but in all other diagnostic features it is similar to Cyclanthera (D. M. Kearns and E. C. Jones 1992).
Fruits of Cyclanthera are usually echinate; only C. pedata (Linnaeus) Schrader and two other species lack spinules. Wild relatives of C. pedata are spiny-fruited and the occurrence of spinules within the species is variable. Cyclanthera pedata is cultivated in Central America and South America for its large, virtually hollow, edible fruits, which are used like bell peppers, mostly to be filled and baked (B. E. Hammel 2009).
SELECTED REFERENCES Jones, C. E. 1969. A Revision of the Genus Cyclanthera (Cucurbitaceae). Ph.D. dissertation. Indiana University. Nesom, G. L. 2014. Taxonomy of Cyclanthera (Cucurbitaceae) in the USA. Phytoneuron 2014-11: 1–17.