Psoralea hypogaea Torr. & A. Gray

Pediomelum hypogaeum (Nutt.) Rydberg
Psoralen hypogaea Nutt.; T. & G. Fl. N. Am. 1: 302. 1838. Lotodes hypogaeum Kuntze, Rev. Gen. 194. 1891.
A subacaulescent perennial, with an oblong-fusiform tuberous root 1-1.5 cm. thick, 2-5 cm. long; stem above ground nearly none; leaves digitately 5-foliolate, clustered at the base; stipules membranous, ovate or lanceolate; petioles 3-10 cm. long, strigose with long appressed hairs; leaflets 2-5 cm. long, 5-7 mm. wide, linear, linear-oblanceolate, or linear-oblong, acute, glabrous or nearly so above, strigose beneath; peduncles usually short, from almost none to 3 cm. long; spikes very dense, 1-3 cm. long; bracts scarious, ovate, acute, hirsute, 5-8 mm. long; calyx hirsute-strigose; tube 4 mm. long; upper four lobes subulate or lance-subulate, 6 mm. long, the lowest one ovate-lanceolate, 8-10 mm. long; corolla about 12 mm. long, similar to that of P. esculentum; pod hirsute, the body ovoid, 5 mm. long, the beak flat, about 8 mm. long; seed light-brown, wrinkled.
Type locality: Plains of the Platte [Nebraska].
Distribution: Nebraska to Montana. Utah, New Mexico, and Oklahoma.

Perennial, Herbs, Stems woody below, or from woody crown or caudex, Taproot present, Tubers or tuberous roots present, Nodules present, Stems very short, acaulescent or subacaulescent, Stems less than 1 m tall, Stems solid, Stems or y oung twigs sparsely to densely hairy, Stem hairs hispid to villous, Leaves alternate, Leaves petiolate, Stipules conspicuous, Stipules green, triangulate to lanceolate or foliaceous, Stipules membranous or chartaceous, Stipules persistent, Stipules free, Leaves compound, Leaves palmately 2-3 foliate, Leaves palmately 5-11 foliate, Leaf or leaflet margins entire, Leaflets 3, Leaflets 5-9, Leaves hairy on one or both surfaces, Inflorescences racemes, Inflorescences spikes or spike-like, Inflorescence axillary, Bracts conspicuously present, Bracts hairy, Flowers zygomorphic, Calyx 5-lobed, Calyx hairy, Petals separate, Corolla papilionaceous, Petals clawed, Petals blue, lavander to purple, or violet, Banner petal ovoid or obovate, Banner petal auriculate, Wing petals narrow, oblanceolate to oblong, Wing petals auriculate, Wing tips obtuse or rounded, Keel tips obtuse or rounded, not beaked, Stamens 9-10, Stamens diadelphous, 9 united, 1 free, Filaments glabrous, Style terete, S tyle hairy, Fruit a legume, Fruit unilocular, Fruit freely dehiscent, Fruit oblong or ellipsoidal, Fruit exserted from calyx, Fruit beaked, Fruit glabrous or glabrate, Fruit hairy, Fruit 1-seeded, Seeds ovoid to rounded in outline, Seed surface smooth, Seeds olive, brown, or black.

Pediomelum hypogaeum (also known as Psoralea hypogaea) is a perennial herb also known as the little Indian breadroot or subterranean Indian breadroot. It is found on the black soil prairies in Texas.