Flora of North America species comparison

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Apios

groundnut
Stems

usually herbaceous, sometimes woody at base, twining or clambering, slightly striate [smooth], glabrous or pubescent.
Leaves

alternate, odd-pinnate;

stipules present, 2, persistent or deciduous, linear-triangular, glabrous or sericeous;

petiolate, petiole striate or smooth;

rachis striate or smooth;

leaflets (3 or)5 or 7(or 9), stipels deciduous or persistent, 2 proximal to terminal leaflet, 1 proximal to lateral leaflets, margins entire, petiolules reduced to pulvinus, blade abaxially pale green, adaxially darker, 47–100 mm, margins entire, glabrous or ciliate, veins anastomosing before margins, surfaces glabrous or pubescent.
Inflorescences

40–70-flowered, axillary, pseudoracemes, nodose, or flowers paired apically in leaf axils, simple or branched;

bracts present, 2, caducous, margins entire, ciliate, surfaces glabrous or pubescent;

bracteoles 2, caducous.
Flowers

papilionaceous;

calyx hemispheric or campanulate, bilobed, lobes 4;

corolla maroon and white, or pale green and rose-purple [yellow-green], 10.5–26 mm;

banner apex fused into stylobos;

keel incurved, narrowly elliptic, connate distally, sometimes slit distally after pollination, narrowly linear to oblong;

stamens 10, diadelphous;

anthers basifixed;

pistil stipitate, disc surrounding and free from stipe;

style spirally coiled;

stigma capitate.
Fruits

legumes, stipitate, cylindric, linear-oblong, apex short-aristate or acuminate, dehiscent, glabrous or pubescent;

endocarp silvery or white [off-white].
Seeds

6–12, elliptic or oblong [circular-oblate], glabrous.
Vines

, perennial, unarmed, latex present, white; rhizomatous, tuber single or several (moniliform) [absent].
x

= 11.

Apios
Distribution
from USDA
North America; Asia
[BONAP county map]
Discussion

Species 5 (2 in the flora).

The term stylobos refers to an involute apical appendage of the banner that holds the keel in place until tripped by a visiting pollinator (J. A. E. Seabrook 1973).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Banners oblate, 10.5–12.5 mm, stylobos 1.5–2 mm; styles glabrous; legumes 6–10(–12) cm; seeds 5–6 mm; corollas deep to pale maroon and white; tubers 4–12, 2–10 cm diam.
A. americana
1. Banners broadly elliptic, 23–26 mm, stylobos 5.8–7.8 mm; styles bearded; legumes 12–15(–18) cm; seeds 7.2–11 mm; corollas pale green and rose-purple; tuber 1, 15–20 cm diam.
A. priceana
Source FNA vol. 11. Author: Michael Woods.
Parent taxa Fabaceae > subfam. Faboideae
Subordinate taxa
A. americana, A. priceana
Name authority Fabricius: Enum., 176. (1759) — name conserved
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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(If the plant you're looking for doesn't show up in the auto-complete list, that means it either isn't described in Flora of North America yet, or it's listed under a synonym. And please note that Flora of North America is still missing several plant families, including Apiaceae, Boraginaceae, and Polemoniaceae.)

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