Plagiocarpus

Taxonomy

Plagiocarpus G. Bentham Hooker's Icon. Pl. 12: 56. Dec 1873.

Subfamily: Faboideae.
Phylogenetic Number: 3.23.03.
Tribe: Bossiaeeae.
Group: Templetonia.
Species Studied - Species in Genus: 1 studied; 1 in genus.

Description

Fruit: A legume; unilocular; 1 cm long; 0.4–0.5 cm wide; 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; oblong; with both sutures nearly straight; not inflated; compressed; without beak; rounded at apex; right-angled with longitudinal axis of fruit; rounded at base; oblique with longitudinal axis of fruit; with the apex and base uniform in texture; ligneous; seed chambers externally invisible; margin not constricted; 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; passive. Replum invisible. Epicarp glossy; multicolored; bichrome (outer margin of valve greenish-brown surrounding a tan inner area); with surface texture uniform; glabrous; without spines; not smooth; with elevated features; veined; reticulately veined (faintly); not tuberculate; faintly wrinkled; not exfoliating; without cracks; without embedded tissue, much thicker than epicarp, running from base to apex. Mesocarp present; thick; surface not veined; 1-layered; without balsamic vesicles; without fibers; without reniform canals; solid; ligneous (sub). Endocarp present; visible; dull; opaque; monochrome; tan; smooth; without adhering pieces of testa; nonseptate; chartaceous; not exfoliating; remaining fused to mesocarp and epicarp; without wings; entire. Seed(s) 1, or 2; length parallel with fruit length; neither overlapping nor touching; in 1 series. Funiculus of 1 length only; thick; curved. Aril present; fleshy; when fleshy cupshaped (if funiculus absent, if present then aril center plugged by a curved, thick stalklike funiculus); entire; covering less than 1/2 of seed; tan.

Seed: 4.5–6.5 mm long; 3–3.8 mm wide; 1.5–3 mm thick; not overgrown; not angular; asymmetrical; elliptic; 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; not adhering to endocarp; free from endocarp; dull; not modified by a bloom; colored; monochrome; greenish to reddish or dark brown; glabrous; smooth (at X 10, see Notes); coriaceous. Pleurogram absent. Pseudopleurogram absent. Fracture lines absent. Rim absent. Raphe visible; from hilum through lens to base of seed and terminating to hilum to lens (and just beyond lens); not bifurcating; color of testa, or lighter than testa, or darker than testa (color of raphe may vary: Between hilum and lens darker than between lens and base of seed); brown; flush. Hilum present; partially concealed, or fully concealed; concealed by funiculus and aril; with faboid split; with the lips of the faboid split the same color as the rest of the hilum; larger than punctiform; 0.9–1 mm long; with curved outline; elliptic; subapical to radicle tip; flush; not within corona, halo, or rim. Lens discernible; 0.5 mm long; with margins curved; roughly circular; not in groove of raphe; adjacent to hilum; 0.6 mm from hilum; slightly mounded; dissimilar color from testa; darker than testa; black; not within corona, halo, or rim. Endosperm present; thin; 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; partially concealing radicle; split over radicle; with lobes; with lobes touching (auriculate); with the interface division terminating at base of radicle; without margins recessed; yellow, or brown; inner face flat; glabrous on inner face. Embryonic axis nearly straight; parallel to length of seed; without a joint evident between the radicle and the cotyledons. Radicle differentiated from cotyledon; bulbose; straight with embryonic axis; centered between cotyledons; less than 1/2 length of cotyledons. Plumule well developed; glabrous.

Distribution

Australia (North Queensland).

Old World; Australia (north Queensland).

Generic Notes

At X 10, The seed coat of Plagiocarpus appears to be smooth. At X 50 (Figure C) the surface of the testa appears to be minutely pitted, and at X 1000 (Figure D) the surface cells of the testa have thick lateral walls with the lumen of the cell appearing as a pit.

Tribal Notes

Tribe Bossiaeeae

The Bossiaeeae with ten genera traditionally has been divided into two groups in part on fruit and seed characters. The Templetonia group with the first four genera (including at the time Lamprolobium, 23.02) has non-winged, coriaceous legumes and compressed seeds bearing a collarlike often-lipped aril (except Templetonia biloba (G. Bentham) R.M. Polhill), and a short, straight radicle. The Bossiaea group with the remaining genera has the legumes keeled to winged or not so, plump seeds often covered by a hooded caplike aril (lacking in Muelleranthus (23.08) and Ptychosema (23.09)), and a slender deflexed radicle exserted from the cotyledons. Crisp and Weston (1987, pages 105–107) in their cladistic analysis of the Bossiaeeae, Brongniartieae (22), and Mirbelieae (24), provided compelling evidence that the Bossiaeeae should be redefined to include only the Bossiaea group (genera 23.05–23.10). The Templetonia group would be moved to the Brongniartieae becoming genera three through eight, after Brongniarta (22.01) and Harpalyce (22.02). The proposed generic sequence would be: 3, Templetonia (23.01); 4, Lamprolobium; 5, Plagiocarpus (23.03); 6, ?Genus A (Templetonia incana J.H. Ross); 7, ?Genus B (Templetonia biloba (G. Bentham) R.M. Polhill); and 8, Hovea (23.04). They (Crisp and Weston, 1995) retracted their proposal to transfer the Templetonia group because of Chappill's (1995) cladistic analysis of the entire family, and we have used the traditional circumscriptions of the two tribes (Pohill, 1994a, 1994b).