3. Cyclanthera gracillima Cogniaux, Diagn. Cucurb. Nouv. 2: 71. 1877.
Slender cyclanthera Slender cyclanthera
Cyclanthera naudiniana Cogniaux var. tenuifolia Cogniaux
Stems glabrous; tendrils unbranched, less commonly 2-branched. Leaves 3- or 5-foliolate, lateral pair of leaflets completely or nearly completely divided to base, petiolules 1–4 mm, terminal leaflet 3–5 cm, blade lanceolate to broadly lanceolate or elliptic-lanceolate, petiolule 5–10 mm, linear, abruptly broadening into leaflet base, leaflet margins coarsely serrate to shallowly lobed; petioles 5–10 mm. Staminate inflorescences 1.5–10.5 cm, floriferous portion 0.2–2.2 cm, 7–26-flowered, racemoid, without lateral branches; flowers solitary or in fascicles of 2–3. Staminate corollas 2.5–2.8 mm diam. Anther heads 0.6–0.8 mm diam., subsessile, glabrous. Fruiting peduncles 2–6 mm. Capsules narrowly ovoid, slightly oblique, short-beaked, 12–25 mm, spinules 2–4[–6] mm.
Flowering Aug–Oct. Canyons, arroyos, canyon walls, slopes, streamsides, riparian woods, sycamore, cottonwood-sycamore-willow, sycamore-Arizona cypress-oak, oak-maple-pine, pine-oak-Arizona cypress, pine-juniper-cottonwood, pine-juniper woodlands; 1400–2000(–2500) m; Ariz., N.Mex.; Mexico.
Cyclanthera gracillima is distinct in its short, few-flowered staminate inflorescence and short fruiting peduncles. The few occurrences in southern Arizona and New Mexico are at the northwesternmost tip of its geographic range. From there it continues southward into Chihuahua and Sonora and then apparently is disjunct to a much broader distribution in the states of central and southern Mexico, from Nayarit and Jalisco to the northeast and southeast.