Strophostyles

Taxonomy

Strophostyles S. Elliott Nom. cons. Sketch Bot. 2: 229. 1823.

Subfamily: Faboideae.
Phylogenetic Number: 3.10.70.
Tribe: Phaseoleae.
Subtribe: Phaseolinae.
Species Studied - Species in Genus: 3 studied; 3 in genus.

Description

Fruit: A legumelegume:
usually dry, dehiscent fruit derived from a single carpel that opens along two longitudinal sutures
; unilocular; 4–7 cm long; 0.5–0.8 cm wide; 0.3–0.5 cm thick; 2–9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with persistent calyx, or deciduous calyx; with calyx shorter than fruit; without orifice formed by curving of fruit or fruit segments; straight to curved (slightly); not plicate; not twisted; symmetrical; linear; not inflated; compressed to terete; without beak; long tapered at apex to tapered at apex; aligned with longitudinal axis of fruit to oblique with longitudinal axis of fruit (slightly); tapered at base to rounded at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture; chartaceous to coriaceous; seed chambers externally invisible, or visible (slightly); seed chambers with the raised seed chambers not torulose; margin not constricted, or constricted; margin slightly constricted along both margins; margin without sulcus; margin plain; wing(s) absent; nonstipitate; with all layers dehiscing; splitting along suture(s). Dehiscence of valves along both sutures; apical and down; active; with valves twisting. Replum invisible. Epicarp dull; monochrome; brown; with surface texture uniform; glabrate, or pubescent and indurate; with hairs appressed (sparse); with 1 type of pubescence; with pubescence golden; with pubescence uniformly distributed; with simple hairs; pliable; with hair bases plain; eglandular; without spines; smooth, or not smooth; with elevated features; not veined; not tuberculate; wrinkled; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; thin; surface not veined; 1-layered; without balsamic vesicles; without fibers; without reniform canals; solid; (sub-) coriaceous to chartaceous. Endocarp present; visible; dull; opaque; monochrome; white; cobwebby to scurfy to floury-filamentous; without adhering pieces of testa; subseptate; osseous; exfoliating in part; remaining fused to mesocarp and epicarp; without wings; entire. Seed(s) 3–8; length parallel with fruit length; neither overlapping nor touching; in 1 series. Funiculus of 1 length only; flattened; straight. Aril present; dry; when dry tongue-aril, or 2-lipped rim-aril (narrow); entire; with tongues (or flap) on lips of 2-lipped rim-aril; with 1 tongue or flap on 1 lip of 2-lipped rim-aril; cream.

Seed: 7.2–10.5 mm long; 3.5–5.5 mm wide; 3.7–5.2 mm thick; not overgrown; angular to not angular; symmetrical; oblong to rectangular; terete; with surface smooth; 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; not adhering to endocarp, or partially adhering to endocarp; free from endocarp; glossy to dull; not modified by a bloom; colored; monochrome, or mottled; with frequent mottles; dark brown; with brown overlay; glabrous; smooth; coriaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Wing(s) absent. Raphe not visible. Hilum present; fully concealed; concealed by funicular remnant; without faboid split; larger than punctiform; 4.2–6.3 mm long; with straight outline; linear; apical according to radicle tip but marginal according to seed length; raised; within rim; rim color of testa, or darker than testa. Lens discernible; 0.8–1 mm long; with margins straight, or curved; linear; circular; not in groove of raphe; confluent with hilum; mounded; same color as testa, or similar color as testa; lighter than testa; brown; within rim, or not within corona, halo, or rim; rim color of testa. Endosperm absent. 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; partially concealing radicle; notched at radicle; without lobes; with the interface division terminating at base of radicle; without margins recessed; white; inner face flat; glabrous on inner face. Embryonic axis oblique; oblique to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; linear; lobe tip curved; oblique to cotyledons; centered between cotyledons; less than 1/2 length of cotyledons. Plumule well developed; glabrous.

Distribution

North America and Mexico.

New World; Canada, United States, and Mexico.

Generic Notes

Yanful and Maun (1996) found fruits of Strophyostyles hevola with up to eight seeds. Fragments of endocarp adhere to the testa which sometimes gives the false impression that it is pubescent.

Tribal Notes

Tribe Phaseoleae

Bruneau et al. (1995) carried out cladistic analyses of tribe Phaseoleae using chloroplast DNA restriction site data. Their results indicated that the tribe is not monophyletic and that the tribal delimitations between Phaseoleae and Desmodieae (11) and between Phaseoleae and Millettieae (7) are problematic.