Dipogon Liebm.

Scientific Description

Family Papilionaceae. Phaseoleae.

Sometimes included in Leguminosae.

Habit and leaf form. Lianas; evergreen, or deciduous; not resinous. Plants unarmed. Plants with neither basal nor terminal concentrations of leaves. Climbing; stem twiners. Twining anticlockwise. Mesophytic. Leaves small to medium-sized; not fasciculate; alternate; spiral, or distichous; not decurrent on the stems; ‘herbaceous’, or leathery; not imbricate; petiolate. Petioles wingless. Leaves non-sheathing; not gland-dotted; compound; pulvinate; ternate. Leaves pinnately trifoliolate. Leaves imparipinnate. Leaflets 3; 2–7 cm long. Lateral leaflets alternate, or opposite. Leaflets stipellate (the stipels subulate, 2–7 mm long); pulvinate; broadly ovate, or triangular (deltate); flat; without lateral lobes. Leaflet margins flat. Leaf blades dorsiventral; cross-venulate. Mature leaf blades adaxially sparsely pubescent (with appressed hairs along the veins and margins); abaxially sparsely pubescent. Leaves with stipules (the stipules narrowly ovate). Stipules intrapetiolar; free of the petiole; free of one another; scaly, or leafy; caducous, or persistent. Leaf blade margins entire; not prickly; flat. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present; glandular hairs absent; complex hairs absent. Branched hairs absent. Stem anatomy. Secondary thickening developing from a conventional cambial ring, or anomalous.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the disk. Entomophilous. Pollination mechanism conspicuously specialized.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; not crowded at the stem bases. Inflorescence few-flowered. Flowers in racemes. Inflorescences simple, or compound. The terminal inflorescence unit cymose, or racemose. Inflorescences axillary; axillary, pedunculate racemose clusters. Flowers pedicellate (the pedicels often recurved); bracteate. Bracts persistent. Flowers (bi-) bracteolate. Bracteoles persistent. Flowers small; very irregular; zygomorphic. The floral asymmetry involving the perianth and involving the androecium. Flowers papilionaceous (imbricate-descending); basically 5 merous; tetracyclic. Floral receptacle with neither androphore nor gynophore. Free hypanthium present, or absent. Hypogynous disk present; intrastaminal. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; lobed; blunt-lobed and toothed (the upper two rounded, the lower three triangular); imbricate; exceeded by the corolla; shallowly bilabiate; neither appendaged nor spurred; non-fleshy; non-accrescent; with the median member anterior. Calyx lobes triangular and orbicular. Corolla present; 5; 1 -whorled; appendiculate (the standard). Standard appendaged (with one large, bilobed appendage between limb and claw). Corolla partially gamopetalous. 4 of the petals joined. The joined petals anterior. The wings of the corolla adherent to the keel; not laterally spurred. Standard ‘normally’ developed; not sericeous. Keel long-acuminate and beaked to not long-acuminate/beaked (acute); neither coiled nor spiralled; not bent and beaked (‘incurved acute’). Corolla imbricate (descending); glabrous abaxially; glabrous adaxially; white, or pink, or purple (and the keel purple-tipped); deciduous; non-accrescent. Petals clawed. Androecial members definite in number. Androecium 10. Androecial members free of the perianth; all equal, or markedly unequal; coherent; 2 - adelphous (the tenth, posterior stamen more or less free of the tube). The staminal tube free from the keel petals. Androecial members 1 -whorled. Androecium exclusively of fertile stamens. Stamens 10; all more or less similar in shape; diplostemonous; both opposite and alternating with the corolla members; filantherous. Anthers connivent; all alike; dorsifixed, or basifixed; versatile, or non-versatile; dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. Pollen shed as single grains. Gynoecium 1 carpelled. The pistil 1 celled. Carpels reduced in number relative to the perianth. Gynoecium monomerous; of one carpel; superior. Carpel stylate; apically stigmatic (and the stigma terminal). Style doubly sigmoid (bent in, out, then in again). Style terete. Style bearded down one side (above, posteriorly, with two rows of hairs). Stigmatic tissue terminal. Carpel 4–8 ovuled. Placentation marginal (along the ventral suture). Gynoecium median. Ovary sessile. Styles hairy. Ovules pendulous to ascending; biseriate; arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.

Fruit and seed features. Fruit aerial; 23–45 mm long; sessile; non-fleshy; not spinose. The fruiting carpel dehiscent; a legume. Pods much elongated; not triangular; straight, or curved; not beaked; not becoming inflated; more or less flat; regularly constricted between adjacent seeds, or not constricted between the seeds; wingless; not internally hairy. Valves of the dehisced pod not twisted. Fruit 1 celled; elastically dehiscent. Dispersal unit the seed. Fruit 4–8 seeded. Seeds non-endospermic; not mucous; compressed; arillate (with a thin expannsion from the funicle); not conspicuously hairy. Cotyledons 2; accumbent. Embryo curved, or bent. Testa hard; non-operculate; smooth; homogeneous in colour. Micropyle zigzag, or not zigzag. Seedling. Germination cryptocotylar.

Special features. Calyx limb 5 lobed. Upper lip of calyx lobed; 2 lobed. Lower lip of calyx lobed; 3 lobed.

Geography, cytology, number of species. Adventive (and cultivated). 2n=22; ploidy levels recorded 2. A genus of 1 species; 1 species in Western Australia; D. lignosus.