Mimosa

Taxonomy

Mimosa C. Linnaeus Sp. Pl. 516. 1 Mai 1753.

Subfamily: Mimosoideae.
Phylogenetic Number: 2.3.27.
Tribe: Mimoseae.
Group: Piptadenia.
Species Studied - Species in Genus: 74 studied; ca. 480 in genus (461 native to the New World).

Description

Fruit: A legume; unilocular; 1–23 cm long; 0.15–3 cm wide; 0.1–0.6 cm thick (excluding prickles up to 3 mm long); 2–9 times longer than wide, or more than 9 times longer than wide; with deciduous androecial sheath; with deciduous corolla; with deciduous calyx; without orifice formed by curving of fruit or fruit segments; straight to curved, or 0.5-coiled to 1-coiled to 1.5-coiled to 2-coiled; not plicate; twisted, or not twisted; asymmetrical, or symmetrical; oblong to obovate, or linear, or falcate, or irregular; with both sutures parallelly curved, or both sutures unequally curved; not inflated; compressed to flattened, or terete to quadrangular; without beak; tapered at apex to rounded at apex (rarely with beak up to 15 mm long); aligned with longitudinal axis of fruit; short tapered at base to rounded at base, or tapered at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture; coriaceous to chartaceous; seed chambers externally visible, or invisible; margin constricted, or not constricted; margin slightly constricted along both margins to constricted along both margins; margin without sulcus; margin plain, or embellished; margin with prickles, or fringe (occassionally both incised winglike); wing(s) absent; stipitate, or substipitate, or nonstipitate (rarely); with the stipe 5–30 mm long; with all layers dehiscing, or with epicarp and mesocarp dehiscing and endocarp not dehiscing, or indehiscent; splitting along suture(s). Dehiscence of valves along both sutures, or 1 suture; medial and up and down (remaining attached to sutures), or apical and down, or basal and up; passive, or active; with valves regularly breaking (into segments and separating from dilated replum). Replum visible (sometimes dilated replum bearing numerous to scattered prickles or unarmed), or invisible. Epicarp dull to glossy; monochrome; brown (to various shades and in combination with other colors), or tan; with surface texture uniform; glabrous to pubescent and indurate; with hairs erect; with simple hairs, or glandular hairs, or complex hairs; with stellate hairs, or setae; eglandular to glandular; with glandular setae; with spines, or without spines; not smooth; with elevated features; often strongly veined; transversely veined relative to fruit length, or 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; brown, or tan; smooth; without adhering pieces of testa; nonseptate to subseptate to septate (segmented fruits); not exfoliating; entire. Seed(s) 1–20; length transverse to fruit length, or oblique to fruit length (basipetal), or parallel with fruit length (basipetal); neither overlapping nor touching, or overlapping (rarely); in 1 series, or 2 or more series (rarely). Funiculus 1.5–5 mm long; of 1 length only; filiform; curved, or contorted. Aril absent.

Seed: 2.3–9 mm long; 1.5–8 mm wide; 1–3 mm thick; not overgrown; not angular; symmetrical; ovate to circular, or elliptic to irregular, or oblong, or rhombic (with or without 1 face of apex and base concaved caused by overlapping seeds); flattened to compressed, or terete (rarely); with surface grooved (2 (rarely 1) longitudinal grooves on each face); longitudinal; 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; free from endocarp; glossy to dull; not modified by a bloom; colored; monochrome, or mottled (rarely); brown (various shades of brown or in combination with other colors to areola lighter colored); with various shades of brown overlay to black overlay (occasionally); glabrous; smooth, or not smooth; with recessed features, or elevated features; blistered cuticle; faintly striate, or concaved (usually 1 face of apex and base); osseous. Pleurogram present (arms not always of equal length and areola width variable); 50–95 %. Pseudopleurogram absent. Fracture lines present, or absent. Rim absent. Wing(s) absent. Raphe not visible. Hilum present; visible, or fully concealed; concealed by funicular remnant; without faboid split; punctiform; subapical to radicle tip; flush; not within corona, halo, or rim. Lens discernible; 0.2–0.5 mm long; with margins curved; elliptic to ovate; not in groove of raphe; mounded to flush, or recessed; same color as testa, or similar color as testa (occasionally surrounded by dark halo); lighter than testa to darker than testa; tan; not within corona, halo, or rim, or within halo (occasionally); halo color darker than testa. Endosperm present; thick to thin; not pluglike and not resembling tip of radicle; adnate to testa. Cotyledons smooth; both outer faces flat; 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; split over radicle; with lobes; with lobes overlapping, or touching (auriculate); with basal groin formed by lobes (when lobes overlap), or without basal groin formed by lobes (when lobes only touch); with the interface division terminating at base of radicle; without margins recessed; inner face flat; glabrous on inner face. Embryonic axis straight; parallel to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; straight with embryonic axis; centered between cotyledons. Plumule well developed to moderately developed; glabrous.

Distribution

Generic Notes

Whereas fruit dehiscence and armature are divisive characters, Seed characters are unifying. Barneby (1991) has synonymized both Schrankia and Schranckiastrum with Mimosa.