This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", 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..
[Apios Moench, Meth. 165. 1794.]
Twining perennial vines, with pinnately 3-7-foliolate leaves, small stipules and rather large brownish-purple or red flowers, mainly in axillary racemes or panicles. Calyx campanulate, somewhat 2-lipped, the 2 lateral teeth very small, the 2 upper united and short, the lower one long and acute. Standard ovate, or orbicular, reflexed. Wings obliquely obovate, adherent to the elongated incurved at length twisted keel. Stamens diadelphous (9 and 1); anthers all alike; ovary nearly sessile; ovules ∞; style slender. Pod linear, straight or slightly curved, compressed, 2-valved, many-seeded. Rootstocks tuberous. [Greek, from the sweet tubers.]
Five known species, the following of eastern North America, 2 of China and 1 of the Himalayas. Type species: Glycine Apios L.
Standard suborbicular, rounded or retuse at the apex; tubers necklace-like.
Standard produced at the apex into a thickened appendage; tubers large, solitary.
Glycine Apios L. Sp. PL 753. 1753.
Apios tuberosa Moench, Meth. 165. 1794.
Apios Apios MacM. Bull. Torr. Club 19: 15. 1892.
Slender, pubescent or glabrate, climbing over bushes to a height of several feet. Rootstock tuberous, the tubers necklace-shaped; stipules subulate, 1"-2" long, deciduous; leaves petioled; leaflets 5-7 (rarely 3), ovate or ovate-lanceolate, acute or acuminate at the apex, rounded at the base, l'-3' long; racemes axillary, often compound; peduncles shorter than the leaves; flowers numerous, brownish purple, odorous, about 6" long; standard not appendaged; rachis of the inflorescence knobby; pod linear, straight or slightly curved, pointed, 2'-4 1/2' long, about 2i" wide, many-seeded, its valves rather coriaceous.
In moist ground, New Brunswick to Florida, west to western Ontario, Minnesota, Nebraska, Kansas and Texas. Stem with milky juice; tubers edible. July-Sept. Ground-, trailing- or potato-pea. Pig-, Dacotah-or Indian-potato. White apple. Traveler's-delight.
Apios Priceana Robinson, Bot. Gaz. 25: 451. 1898.
Tuber often 6'-7' thick, somewhat higher than thick, solitary. Stems pubescent with reflexed hairs, or glabrous, 3°-10° long; leaflets 3-9, ovate or ovate-lanceolate, 4' long or less, acuminate at the apex, rounded or obtuse at the base, sparingly pubescent on both sides; panicles often 2 or 3 together in the axils, many-flowered, 4'-6' long; corolla greenish-white, tinged with rose or magenta; blade of the standard about 1' long, produced at the apex into a spongy or fleshy knob; pods linear, 4'-5' long.