OLACACEAE

370

DICOTYLEDONEAE

372 DICOTYLEDONEAE

liculate; blades ovate, elliptic or obovate, acute to acumi- nate at apex, acute at base, 3.5-18 cm long, 2-7.5 cm wide, subcoriaceous, the major lateral veins in 6-9 pairs, conspicuous below, distinctly lighter than the surround- ing tissue. Flowers greenish, ca 2.5 mm long; pedicels ca 5 mm long, clustered in axillary fascicles; calyx shal- low, accrescent in fruit, the lobes 5, acute; petals 5, green- ish, valvate, boat-shaped; stamens 10, shorter than petals, included; filaments strap-shaped, narrowed just below anther; anthers ca 0.3 mm long and wide; ovary ovate.

Fuiting calyces about as long as drupe, ca 2 cm broad, red, shallowly 5-lobed or undulate; drupes ellipsoid, ca

1 cm long, black. Croat 4532, 6052.

Common in the forest, especially the old forest. Flow- ers principally from April to July (especially in May and June). The fruits develop to mature size by July, but mostly in August and September.

Costa Rica to Colombia. In Panama, widespread;

most common at low to middle elevations; known from tropical moist forest in the Canal Zone, Colon, Chiriqui, and Darien, from premontane wet forest in Veraguas, Code, Panama, and Darien, and from tropical wet forest in Colon and Code. *

44. ARISTOLOCHIACEAE Lianas, the younger stems herbaceous. Leaves alternate, petiolate, simple; blades entire, somewhat pubescent;

venation pinnate (may be subpinnate at base); stipules lacking; pseudostipules lacking (in ours). Flowers proto- gynous, bisexual, apetalous, zygomorphic, solitary in the leaf axils or on short racemes; calyx tubular, consisting of 3 united sepals, inflated at the base (the inflated part called the utricle), expanded at the limb, showy, the tube forming an annulus where it meets the limb and also forming an inverted narrowed structure on the lower end (the syrinx), which extends into the utricle; petals lack- ing; styles, stigmas, and stamens united in a crownlike gynostegium; stamens 6, adnate to the style; anthers 4-celled, extrorse, dehiscing longitudinally; ovary infer- ior, 6-loculate; placentation axile; ovules several to many per placenta, anatropous; styles 6, forming subcapitate, stigmatic lobes. Fruits capsules; dehiscence acropetal, septifragal; seeds numerous, flat, with copious endosperm.

Distinguished by their unusual flowers and fruits. The complex flower is a greatly modified calyx. For a descrip- tive account of flower morphology refer to Pfeifer (1966).

Pollinated by insects, usually flies (Diptera), which are

attracted to the flowers by a carrionlike odor and the intense colors (usually purplish). The corolla tube has rigid retrorse trichomes on the first day after opening when the stigmas are receptive (Petch, 1924; Corner, 1964). The pollinators are prevented from leaving the flower by these trichomes, so they find their way to the utricle. The following day the anthers dehisce, shedding pollen on the insect, and the retrorse trichomes wilt, allowing the insect to escape carrying the pollen.

For a description of typical seed dispersal, see the discussion of Aristolochia chapmaniana.

Ten genera and about 450 species; primarily in the tropics but extending to most temperate regions.

ARISTOLOCHIA L.

Aristolochia chapmaniana Standl., Contr. Arnold Arbor. 5:60. 1933

Twining liana, sparsely hispidulous; trunk corky and deeply fissured near ground, to ca 5 cm diam. Leaves alternate; petioles 8-22 mm long; blades oblong-spatulate, acute to obtuse at apex, deeply cordate at base, 10-20 cm long, 3-6 cm wide, glabrate above, inconspicuously short-pubescent below. Flowers solitary, axillary, usually slightly arched, dark purple-brown; calyx expanded into a narrow ellipsoid balloon ca 6 cm long, then constricted into a tube ca 3.5 cm long, the tube split on one side to form an oblong-lanceolate limb to 7 cm long; corolla lacking; stamens 6, the anthers sessile and adnate to style; styles 6, connate; stigmas capitate. Capsules ovate- cylindrical, prominently 6-ribbed, 10-12 cm long, ca 5 cm wide, on a long stipe, dehiscing from apex to base, the 6 valves spreading widely to disperse seeds but re- maining attached on both ends, the inner valves diverging through outer valves at apex and attached to outer valves by a ladderlike series of fibers, the fibers acting to slow dispersal of seeds; seeds very numerous, flattened, stacked in 6 vertical rows, the seminiferous part cordate, ca 5 mm diam, bearing 2 unequal pairs of lateral wings ca 2 cm wide, the sides of the wings ± rounded, the longer pair ca 1.2 cm long, the shorter pair ca 0.8 cm long. Croat 5958, Shattuck 413 (type).

Occasional, in the forest and along the shore. Flowers from at least November to January. The fruits, with some seeds, reported from April to September. Capsules may hang on all year.

Central America and northern South America. In Panama, known from tropical moist forest in the Canal

KEY TO THE SPECIES OF ARISTOLOCHIA

Plants conspicuously pilose on most parts; limb of calyx less than 3 cm long; capsules ovoid, ca 6 cm long A. pilosa H.B.K.

Plants not pilose; limb of calyx more than 3 cm long; capsules ± cylindrical:

Blades deeply and narrowly cordate at base, scarcely if at all broader at base; calyx limb narrow, ca 7 cm long A. chapmaniana Standl.

Blades truncate or shallowly and broadly cordate at base, conspicuously ovate; calyx limb 10-20 cm long A. gigantea Mart. & Zucc.

374

DICOTYLEDONEAE

Zone and Panama and from premontane wet forest in Code.

See Figs. 215 and 216.

Aristolochia gigantea Mart. & Zucc, Nov. Gen. Sp.

PL 1:75, t. 48. 1824 A. sylvicola Standl.

Zaragosa

Twining liana, glabrous but the leaf blade below arach- noid-pubescent. Leaves alternate; petioles slender, ca 4-6 cm long; blades ovate, acuminate, truncate to shal- lowly cordate at base, 10-15 (20) cm long, 7-11 (12) cm wide, grayish below with arachnoid trichomes. Flowers in short racemes of few flowers, white, densely speckled with pink and maroon; calyx expanded into a ± campan- ulate balloon to 8 cm long, constricted into a short, re- flexed tube opening into a large limb to 20 cm long;

corolla lacking; stamens 6, the anthers sessile and adnate to style; styles 6, ± connate; stamens capitate. Capsules cylindrical, to 13 cm long and ca 3 cm wide, dehiscing from base, bearing many seeds; seeds 7-8 mm long, flattened, elliptic, the margins bordering a prominent medial rib, very revolute, the dehisced valves ca 1.5 cm wide. Croat 11260, Shattuck 640.

Rare, in the forest. Some flowers have been seen in September and December. Maturity time of the fruits is uncertain, probably in the dry season.

Known only from Panama, in tropical moist forest in the Canal Zone and Bocas del Toro and from tropical wet forest in Darien.

Aristolochia pilosa H.B.K., Nov. Gen. & Sp. 2:146, t.

113. 1817

A. costaricensis (Klotzsch) Duch.

Slender, twining liana, conspicuously pilose on most parts. Leaves alternate; petioles slender, to 7 cm long;

blades ovate, acute at apex, deeply cordate at base, 6-25 cm long, 5-15 cm wide, glabrescent above. Flowers solitary in axils, speckled white and brownish-purple;

calyx expanded into a short ellipsoid balloon to 3 cm long, then constricted obliquely into a campanulate tube ca 2.5 cm long, finally opening into a narrow, fringed limb 1.5-2.5 cm long; corolla lacking; stamens 6, the anthers sessile and adnate to style; styles 6, connate;

stigmas capitate. Capsules ovoid, ca 6 cm long and 4 cm wide, dehiscing from base, bearing many seeds; seeds disk-shaped, ca 1 cm diam. Croat 9011.

Occasional, around the Laboratory Clearing. Flowers mostly from January to May, sometimes later in the rainy season also. The fruits have not been seen on the island.

Central America and northern South America. In Panama, known from tropical moist forest in the Canal Zone, Bocas del Toro, Panama, and Darien.

See Fig. 217.