This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Perennial herbs or twining vines. Leaves alternate, mostly petioled and entire (some exotic species 3-7-lobed), cordate, palmately 3-many-nerved. Flowers irregular, solitary or clustered. Calyx adnate to the ovary, at least to its base, the tube narrow, usually inflated around the style and contracted at the throat, the limb spreading or reflexed, entire, 3-6lobed or appendaged. Stamens mostly 6; anthers sessile, adnate to the short style or stigma, 2-celled, the sacs longitudinally dehiscent. Ovary partly or wholly inferior, mostly 6-celled with 6 parietal placentae. Style 3-6-lobed. Capsule naked, septicidally 6-valved.
Seeds very numerous, horizontal, compressed, their sides flat or concave. [Named for its supposed medicinal properties.]
About 200 species, widely distributed in tropical and temperate regions. Besides the following, some 6 others occur in the southern and western United States. Type species: Aristolochia rotunda L.
Calyx-tube bent; flowers solitary, on basal scaly branches.
Calyx-tube straight; flowers axillary, clustered.
Long twining vines; flowers axillary; calyx-tube bent.
Leaves minutely pubescent; calyx-limb flat, spreading.
Leaves tomentose; calyx-limb rugose, reflexed.
Aristolochia Serpentaria L. Sp. PI. 961. 1753.
A perennial pubescent nearly erect herb, 10' -3o tall, with short rootstocks and fibrous aromatic roots. Leaves ovate, ovate-lanceolate or oblong-lanceolate, thin, green on both sides, acuminate at the apex, cordate or hastate at the base, 1 1/2'-5' long, 1/2'-2 wide; petioles 1/4'-1' long; lowest leaves reduced to scales; flowers solitary and terminal, on slender basal scaly branches; tube of the calyx curved like the letter S, enlarged at the ovary and at its throat, the Emb short, spreading, slightly 3-lobed; anthers contiguous in pairs; stigma 3-lobed; capsule subglo-bose, ridged, about ¥ in diameter. Flowers sometimes cleistogamous.
In dry woods, Connecticut and New York to Michigan, Florida, Louisiana and Missouri. Ascends to 2500 ft. in Virginia. June-July. Fruit ripe Sept. Sangrel snakeweed. Sangree-root. Black snakeroot. Pellican-flower.
Aristolochia Clematitis L. Sp. PI. 962. 1753.
Herbaceous, perennial; stem erect, glabrous, zigzag, striate, 1°-2° tall. Leaves dark green, reniform, subacute or obtuse at the apex, glabrous or their margins minutely spinulose-ciliatc, strongly reticulate-veined, 2'-5' wide; petioles shorter than the blades; flowers fascicled in the axils, l'- l 1/2' long; tube of the calyx yellowish green, straight, enlarged around the ovary, the 6 lobes appendaged; anthers equidistant.
Roadsides and thickets, New York to Maryland. Escaped from cultivation. Native of southern Europe. Summer. Upright birthwort.
A twining vine, the stem sometimes 1' in diameter and 300 long, the branches very slender, terete, green, glabrous. Leaves thin, broadly reniform or suborbicular, densely pubescent beneath when young, glabrous or nearly so and 6'-is' broad when mature; petioles slender, 1'-4' long; peduncles solitary or 2 or 3 together in the axils, about as long as the petioles, each with a suborbicular clasping bract at about the middle 1/2'-1' in diameter; calyx-tube strongly curved, 1' or more long, inflated above the ovary, contracted at the throat, yellowish-green, veiny, the limb flat, spreading, purple-brown, somewhat 3-lobed; anthers contiguous in pairs under the 3 lobes of the stigma; capsule oblong-cylindric, strongly parallel-nerved, 2-3' long, 8"-10" in diameter.
A. tomentosa Sims, Bot. Mag. pl. 1369. 1811.
A twining vine, similar to the preceding, but the twigs, petioles, leaves and peduncles persistently tomentose. Leaves suborbicular or broadly ovate, obtuse or rounded at the apex, 3'-6' broad when mature; petioles rather stout, 1'-3,' long; peduncles axillary, mostly solitary, slender, bractless; calyx densely tomentose, the tube sharply curved, yellowish-green, about 1 1/2' long, its throat nearly closed, the limb becoming reflexed, wrinkled, dark purple, 3-lobed; anthers contiguous in pairs beneath the 3 spreading lobes of the stigma; capsule oblong-cylindric.
In woods, Missouri and southern Illinois to North Carolina, Kansas, Arkansas, Alabama and Florida. May-June.