Pycnospora Wight & Arn.
Prodr.Fl.Ind.Orient. 1:197 (1834)

Name Status: Current
Browse to the list of specimens for Pycnospora Wight & Arn.

Scientific Description
Leslie Watson, Thursday 8 September 2016

Family Papilionaceae. Desmodieae.

Habit and leaf form. Erect or spreading (sub-) shrubs, or herbs. Plants unarmed. Perennial. Mesophytic. Leaves small to medium-sized; not fasciculate; alternate; spiral; ‘herbaceous’, or leathery; not imbricate; petiolate. Petioles wingless. Leaves non-sheathing; compound; pulvinate; ternate (unifoliolate only at the base of the plant). Leaves pinnately trifoliolate. Leaves imparipinnate. Leaflets 1, or 3. Lateral leaflets opposite. Leaflets stipellate; pulvinate, or epulvinate; flat, or folded; without lateral lobes. Leaf blades dorsiventral; cross-venulate. Leaves with stipules. Stipules intrapetiolar; free of one another; not ochreate; scaly (membranous). Leaf blade margins entire; flat. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present (with simple and hooked hairs). Stem anatomy. Nodes tri-lacunar, or penta-lacunar. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; often in pairs, subtended by a common bract; in racemes, or in panicles (rachis and calyces glandular-hairy). Inflorescences compound (pedicels paired). The terminal inflorescence unit cymose, or racemose. Inflorescences terminal. Flowers pedicellate. Pedicels flattened. Flowers bracteate. Bracts deciduous (caducous, striate). Flowers ebracteolate; small; very irregular; zygomorphic; not resupinate. The floral asymmetry involving the perianth, or involving the perianth and involving the androecium. Flowers papilionaceous (imbricate-descending, with the posterior petal outside and forming the ‘standard’); basically 5 merous. Floral receptacle with neither androphore nor gynophore. Free hypanthium present, or absent. Hypogynous disk present; intrastaminal; annular. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; 5 lobed. Calyx lobes about the same length as the tube to markedly longer than the tube. Calyx imbricate, or valvate; exceeded by the corolla; bilabiate (the posterior pair of members connate for all or much of their length); non-fleshy; persistent; non-accrescent; with the median member anterior. Epicalyx absent. Corolla present; 5; 1 -whorled; appendiculate to not appendiculate (the keel petals narrowly appendaged on either side). Standard not appendaged. Corolla partially gamopetalous. 4 of the petals joined (the two ventral petals connivent to form the ‘keel’, the wings adhering to the keel). The joined petals anterior. The wings of the corolla adherent to the keel; not laterally spurred. Standard ‘normally’ developed (not reflexed); not sericeous. Keel shorter than standard; not long-acuminate/beaked; neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); pink, or purple, or violet, or blue (lilac); deciduous; non-accrescent. Petals clawed (only the wings and keel clawed, the standard sessile). Androecial members definite in number. Androecium 10. Androecial sequence determinable, or not determinable. Androecial members free of the perianth; markedly unequal (the filaments alternately long and short); coherent (basally, into a tube); 1 - adelphous, or 2 - adelphous (the vexillary stamen connate high up with the rest, or at length free). The staminal tube free from the keel petals. Androecial members 1 -whorled (although diplostemonous). Androecium exclusively of fertile stamens. Stamens 10; all more or less similar in shape; diplostemonous; both opposite and alternating with the corolla members. Anthers separate from one another, or connivent; all alike; dorsifixed (but near the base); versatile; dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. Pollen shed as single grains (tricolporate). Fertile gynoecium present. 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. Style (in-) curved. Style hairy but not bearded (hairy towards the base only), or glabrous. Stigmatic tissue terminal. Carpel 5–15 ovuled (? — several). Placentation marginal. Gynoecium median (the placenta posterior, on the ventral suture). Ovary sessile. Ovary summit hairy, the hairs not confined to radiating bands (hirsute). Stigmas capitate. Ovules pendulous to ascending; biseriate; arillate, or non-arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.

Fruit and seed features. Fruit sessile; non-fleshy; hairy; not spinose. The fruiting carpel dehiscent; a legume (black when mature). Pods somewhat elongated, or much elongated (ellipsoid); not triangular; straight; becoming inflated; terete; not constricted between the seeds; not transversely septate; wingless. Fruit 1 celled; 4–6 seeded. Seeds reniform; endospermic, or non-endospermic; not mucous; small; non-arillate. Cotyledons 2; accumbent. Embryo curved, or bent (the radicle inflexed). Testa non-operculate; conspicuously colour-patterned (dark mottled). Micropyle zigzag, or not zigzag. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Nitrogen-fixing root nodules present. Aluminium accumulation not found. Photosynthetic pathway: C3.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. 2n=(20), 22. A genus of 1 species; 1 species in Western Australia.

Taxonomic Literature

  • Wheeler, J. R.; Rye, B. L.; Koch, B. L.; Wilson, A. J. G.; Western Australian Herbarium (1992). Flora of the Kimberley region. Western Australian Herbarium. Como, W.A.