Petalostylis

Taxonomy

Petalostylis R. Brown In Sturt, Exped. Centr. Australia 2: app. 79. 1849.

Subfamily: Caesalpinioideae.
Phylogenetic Number: 1.2.20.
Tribe: Cassieae.
Subtribe: Labicheinae.
Species Studied - Species in Genus: 2 studied; 2 in genus.

Description

Fruit: A legume; unilocular; 2.5–3 cm long; 0.8–0.9 cm wide; 0.2–0.3 cm thick; 2–9 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; not plicate; not twisted; asymmetrical; rhombic; not inflated; compressed; without beak; long tapered at apex; aligned with longitudinal axis of fruit; short tapered at base; aligned with longitudinal axis of fruit; with the apex and base uniform in texture; coriaceous; seed chambers externally visible; margin not constricted; margin without sulcus; margin plain; wing(s) absent; substipitate; with all layers dehiscing; splitting along suture(s). Dehiscence of valves along both sutures (?); apical and down; active; with valves enrolling. Replum invisible. Epicarp dull; monochrome; brown; with surface texture uniform; glabrous, or pubescent and indurate; with hairs erect; with simple hairs (?); eglandular; without spines; not smooth; with elevated features; not veined; not tuberculate; blistered; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; surface not veined; 1-layered; without balsamic vesicles; without fibers; without reniform canals; solid; coriaceous ("thin"). Endocarp present; visible; dull; opaque; monochrome; greenish yellow; cobwebby ("mixture of tissue and hairs); without adhering pieces of testa; subseptate; not exfoliating; remaining fused to mesocarp and epicarp; entire. Seed(s) 4–6; length oblique to fruit length; neither overlapping nor touching; in 1 series. Funiculus 0.1–0.5 mm long; of 1 length only; thick; straight to triangular. Aril present (honey colored); fleshy; when fleshy cupshaped; entire; covering less than 1/2 of seed ("up to 0.1 mm long").

Seed: 4–4.5 mm long; 2.5–2.8 mm wide; 2 mm thick; not overgrown; not angular; symmetrical; oblong linear; compressed; 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; free from endocarp; glossy; not modified by a bloom; colored; mottled; brown (greenish and dark); with brown overlay; glabrous; smooth; osseous. Pleurogram absent. Pseudopleurogram absent. Fracture lines present; inconspicuous transverse, or longitudinal (prominent from hilum to base). Rim absent. Wing(s) absent. Raphe visible ("color of mottles border by nonmottled testa extending from hilum through lens to base of seed"). Hilum present; fully concealed; concealed by aril, or aril remnant; without faboid split; larger than punctiform; 0.1–0.4 mm long; with curved outline; elliptic; apical at apex of radicle tip; raised; not within corona, halo, or rim. Lens discernible; 0.1–0.4 mm long; with margins curved; elliptic (along margin at right angles to hilum and above middle of seed); not in groove of raphe; mounded; same color as testa (dark brown); not within corona, halo, or rim. Endosperm present; thick; not pluglike and not resembling tip of radicle; adnate to embryo. 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; with lobes; with lobes not touching; with the interface division terminating at base of radicle; without margins recessed; inner face flat; glabrous on inner face. Embryonic axis straight; oblique to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; centered between cotyledons. Plumule rudimentary; glabrous.

Distribution

Australia.

Old World; Australia.

Generic Notes

The number of species in the genus is based on Symon (1981) and Ross (1986), not on Irwin and Barneby (1981).