Pediomelum

Taxonomy

Pediomelum P.A. Rydberg N. Amer. Fl. 24: 17. 25 Apr 1919.

Subfamily: Faboideae.
Phylogenetic Number: 3.12.03.
Tribe: Psoraleeae.
Species Studied - Species in Genus: 4 studied; 21 in genus.

Description

Fruit: A legume; unilocular; 0.8–1.6 cm long (including beak); 0.4–0.5 cm wide; 0.2–0.25 cm thick; length less than twice as long as width to 2–9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with persistent calyx; with calyx shorter than fruit (but not beak); without orifice formed by curving of fruit or fruit segments; straight; not plicate; not twisted; asymmetrical, or symmetrical (except beak); oblong; with both sutures parallelly curved; not inflated; compressed; with beak; straight; with solid beak the same color and texture as fruit; long tapered at apex, or rounded at apex; aligned with longitudinal axis of fruit to oblique with longitudinal axis of fruit; rounded at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture, or differing in texture; upper 3/4 barely inflated, reticulate, and pubescent and lower 1/4 not inflated, reticulate, or pubescent; chartaceous, or fragile, thinner than chartaceous, like Trifolium; seed chambers externally visible; margin not constricted; margin without sulcus; margin plain, or embellished; margin with thickened sutural areas (thickened margins); wing(s) absent; substipitate, or nonstipitate; indehiscent. Replum invisible. Epicarp dull; monochrome; red, or tan; with surface texture uniform; pubescent and indurate; with hairs erect; with 1 type of pubescence; villous; with pubescence gray; with pubescence uniformly distributed; with simple hairs; pliable; with hair bases plain; glandular, or eglandular; with glandular dots; limited to a portion of fruit; upper 3/4 glandular and lower 1/4 eglandular; without spines; not smooth; with elevated features; veined; reticulately veined; not tuberculate; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp absent. Endocarp present; visible; dull; opaque; monochrome; tan; smooth; without adhering pieces of testa; nonseptate; chartaceous; not exfoliating; remaining fused to epicarp; without wings; entire. Seed(s) 1; length parallel with fruit length. Funiculus less than 1 mm long; straight. Aril absent.

Seed: 4.5–6 mm long; 2.8–4 mm wide; 1.5–2.5 mm thick; not overgrown; not angular; symmetrical, or asymmetrical; oblong; compressed; without visible radicle and cotyledon lobes; without hilar sinus; without umbo on seed faces; without medial ridge on each face. Cuticle not exfoliating; not inflated; not wrinkled. Testa present; without pieces of adhering epicarp; partially adhering to endocarp (may have); free from endocarp; glossy; not modified by a bloom; colored; monochrome, or streaked; with frequent streaks; green (ish), or red (brownish), or tan, or yellow; with black overlay (faintly), or brown overlay; glabrous; smooth (P. cyphocalyx (A. Gray) P.A. Rydberg), or not smooth; with elevated features, or recessed features; wrinkled (P. castoreum (S. Watson) P.A. Rydberg); pitted with small separate pits (faintly and widely scattered); coriaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Raphe not visible. Hilum present; fully concealed; concealed by funicular remnant; with faboid split; with the lips of the faboid split the same color as the rest of the hilum; larger than punctiform; 0.3–0.6 mm long; with curved outline; circular, or elliptic; marginal according to radicle tip; recessed; within corona, or not within corona, halo, or rim; corona color lighter than testa. Lens discernible; 0.1–0.5 mm long; with margins straight, or curved; linear, or oblong; circular, or oblong; not in groove of raphe; adjacent to hilum; 0.1–0.2 mm from hilum; mounded; dissimilar color from testa; darker than testa; black; not within corona, halo, or rim. Endosperm present; thin (thinnest of all genera in tribe); not pluglike and not resembling tip of radicle; covering entire embryo; adnate to testa. Cotyledons smooth; both outer faces convex; both the same thickness; both more or less of equal length; not folded; margin entire 180 degrees from base of radicle; similar at apex; not concealing radicle; entire over radicle; without lobes; with the interface division terminating in radicle tissue; without margins recessed; tan; inner face flat; glabrous on inner face. Embryonic axis deflexed; parallel to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; linear; deflexed and parallel to cotyledon length; centered between cotyledons; 1/2 to nearly length of cotyledons. Plumule rudimentary; glabrous.

Distribution

North America, Mexico, and Central and South Africa.

New World; United States to Mexico to West Indies to Central America to South America.

Generic Notes

Grimes (1990) recognized 21 species, and we are following his count. Pediomelum argophyllum (F.T. Pursh) J. W. Grimes and P. castoreum have beaks like Bitumaria (12.02), but their fruits are too fragile and too few in number in our sample to be completely analyzed.

Tribal Notes

Tribe Psoraleeae

Stirton (1981) illustrated seeds and fruits of Amorpheae and Psoraleeae. Since Isely (1962) monographed the tribe for north-central United States the spelling of the tribe name has changed as well as the genera recognized in the tribe. Amorpha (6.04), Dalea (6.08) and Petalostemon A. Michaux (now part of Dalea) are now in the Amphoreae (6), and species in the remaining genus, Psoralea (12.09), have been assigned to several genera treated here. Grimes (1990) noted that this tribe "has been described as having indehiscent fruits. However, in many North American species the fruit is secondarily dehiscent (that is, not along sutures) by transverse rupture of the pod." This technically is not dehiscence.