Cardiospermum halicacabum L., heartseed vine, common balloonvine, farolitos. Perennial herbaceous vine, tendrilar, deep–taprooted, several–stemmed at base, long branches often unbranched, growing on itself and surrounding plants to prostrate and trailing on bare ground; shoots with only cauline leaves, flexible–stemmed; tendril axillary, produced at base of emerging inflorescence or itself with a terminal 3–branched inflorescence, slender, several–ridged and often 3–sided, basal axis 30—45 × 0.5 mm, yellow–green, swollen at base and often ⊥ stem, forked at the top with an opposite pair of coiled branches, the branches hemi–cylindric flat on the upper side, with pulvinus on upper side, having bracts at branches, bracts awl–shaped like stipules.
Stems strongly 5–ridged, to 3 mm in diameter, with 3 ridges descending from each leaf, yellow–green, ± tough, internodes to 55 mm long, short–hairy with hairs arched upward
Leaves helically alternate, 2–compound 3–foliolate (biternate), petiolate, with stipules; stipules 2, narrowly triangular to awl–shaped, ca. 1 mm long, sparsely short–ciliate on margins; petiole channeled and ridged, to 28 mm long, sparsely short–strigose; blade ovate in outline, to 80 mm long, stipels of primary leaflets absent, petiolule of primary leaflets with a central ridge and pair of winglike margins having photosynthetic tissue, 3—17 mm long, of terminal leaflet > lateral leaflets, secondary leaflets sessile, narrowly ovate to lanceolate in outline, to 45 × 22 mm, of lateral secondary leaflets asymmetric and < terminal secondary leaflet ca. 1.5×, thin and easily wilted, long–tapered at base, coarsely serrate and lobed, the deepest sinuses never reaching midrib, with teeth acute to rounded and having a pale green callus at tip, acuminate to acute at tip, pinnately veined with principal veins raised on lower surface, surfaces dull with scattered, upward–pointing short hairs, principal lateral veins ending at tip of tooth or lobe, the lowest pair of lobes on lateral leaflets rounded with a gland at tip; prophyll (bract subtending lateral shoot near base of tendril) awl–shaped, < 1 mm long
Inflorescence umbel–like or racemelike cyme, terminal from between pair of tendril branches, several–flowered and flowers overlapping (short axis internodes) and crowded on racemelike tip, 3–forked superficially appearing whorled, bracteate, glabrous; peduncle 4—7 mm long, 3–forked at top; bract subtending each branch above fork, awl–shaped to triangular, 1.1—1.4 mm long; branchlets < peduncle, with pulvinus at base, flattish on inward–facing side above pulvinus; bractlet subtending pedicel awl–shaped, 0.8—1 mm long, decreasing upward, appressed to persistent basal, longer portion of pedicel, glabrous; pedicel at anthesis 2.5—3 mm long with abscission zone < tip of bractlet, pale green, glabrous.
Flower bisexual, bilateral, 6—7 mm across (vertically); sepals 4, opposite decussate, dimorphic, greenish, palmately veined, outer, lateral pair ascending, smaller, ± roundish or shallowly notched, ca. 2 × 1.5 mm, margins and tip whitish and sometimes on outer surface minutely purplish spotted, inner, pair spreading, ± cupped to boat–shaped (acute–obovate), 3.5—4.5 × 2.5—3 mm, upper sepal enclosing lower sepal in bud; petals 4, overlapping in bud, ± fan–shaped, ca. 3.6 × 1.9 mm, white (pale yellow in bud), with appendage, truncate to shallowly notched at tip, the appendages attached near base on inner surface and petal–like, appendages of 2 upper petals ± ovate to heart–shaped and asymmetric, with partition near midline and wavy margins, ca. 2/3—3/4 length of petal, inconspicuously hairy at base, appendages of 2 lower petals (next to lower sepal) scalloped to reflexed–lobed and bright yellow (white below yellow), ca. 2 mm long, conspicuously short–villous and adherent with hairs; glands attached to base of sepals below bases of stamens, projections ca. 0.25 mm long, pale green but at anthesis colorless; stamens 8 in 2 whorls, 3 lower stamens, 3 on one side, 2 on other side; filaments appressed to 3–sided ovary, flattened front–to–back and tapered to tip, 1.4—1.7 mm long, pale white aging pink, channeled on inner side, short–ciliate above midpoint, conspicuously papillate; anthers dorsifixed, dithecal, 0.4—0.7 mm long, white, arrow–shaped at base, longitudinally dehiscent; pollen white; nectary below ovary mostly on the lower side, platform with 2 projections; pistil 1; ovary superior, 3–sided and 3–angled, ellipsoid in outline, ca. 2.3 × 1.3 mm, yellow–green, short–hirsute along edges, 3–chambered, each chamber with 1 ovule on an ascending stalk with an enlarged funiculus, ovule greenish; style arising at right angles with 3 descending branches from midpoint, ca. 1 mm long; stigma positioned close to anthers.
Fruit capsule, conspicuously inflated, loculicidal, 3–chambered, 1—3–seeded, obovoid 3–lobed, ca. 25—30 × 25—30 mm, papery brown and veiny, short–stalked (on carpophore) with stalk short–hairy, lobes rounded and uniformly short–pilose, with slender ridges and short–ciliate, depressed at top; persistent 4 sepals obovate, 1.7—2 × 1.4—2 mm; with persistent style and stigmas.
Seedspheroid, 4—4.3 mm, glossy bright green aging dull black, smooth; aril pale broadly heart–shaped aril on the lower 1/3 of seed, pale yellow and minutely roughened.
A. C. Gibson