Ptychosema Benth.
Edwards's Bot.Reg. (1839)

Name Status: Current
Browse to the list of specimens for Ptychosema Benth.

Scientific Description
Leslie Watson, Thursday 8 September 2016

Family Papilionaceae. Bossiaeae.

Habit and leaf form. Diffuse herbs. Annual; plants with neither basal nor terminal concentrations of leaves. Mesophytic, or xerophytic. Leaves minute to medium-sized; alternate; spiral, or distichous; leathery, or membranous; not imbricate; petiolate to sessile; non-sheathing; compound; pulvinate; ternate, or pinnate (usually). Leaves when trifoliolate, palmately trifoliolate. Leaves when pinnate, imparipinnate. Leaflets (3–)7–13. Lateral leaflets opposite. Leaflets not stipellate; pulvinate, or epulvinate; without lateral lobes. Leaf blades dorsiventral, or isobilateral, or centric. Leaves with stipules. Stipules intrapetiolar; small; caducous, or persistent. Leaf blade margins entire. Leaves without a persistent basal meristem. Stem anatomy. Nodes tri-lacunar, or penta-lacunar. Secondary thickening absent, or developing from a conventional cambial ring.

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

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; not crowded at the stem bases; when solitary, terminal (on long peduncles); when aggregated, in racemes. Inflorescences simple. The terminal inflorescence unit racemose. Inflorescences terminal, or leaf-opposed. Flowers bracteate (the bract minute, lanceolate, those of solitary flowers accompanied by a bractlike rachis extension); (bi-) bracteolate (but without a series of subtending scales). Bracteoles not adnate to the receptacle (on the upper part of the pedicel). Flowers minute to medium-sized; operculate (calyptrate), or not operculate; somewhat irregular to very irregular; zygomorphic. 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 a flag (‘standard’)); basically 5 merous. Floral receptacle with neither androphore nor gynophore. Free hypanthium present (well developed), or absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; (4–5) lobed. Calyx lobes about the same length as the tube. Calyx imbricate, or valvate; exceeded by the corolla; bilabiate (the lobes subequal in length, but the posterior pair somewhat larger and connate into an emarginate upper lip); persistent; with the median member anterior. Epicalyx absent. Corolla present; 5; 1 -whorled; appendiculate, or not appendiculate. Standard not appendaged. Corolla polypetalous, or partially gamopetalous. 2 of the petals joined (the two ventral petals connivent to form the ‘keel’). The joined petals of the papilionate corolla anterior. The wings of the corolla free from the keel; not laterally spurred. Standard ‘normally’ developed (suborbicular); emarginate. Keel conspicuously exceeded by the wings (almost straight, the wings falcate-oblong); not long-acuminate/beaked (blunt); neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); violet; persistent, or deciduous. Petals rather long clawed. Androecial members definite in number. Androecium 10. Androecial sequence determinable, or not determinable. Androecial members free of the perianth; all equal, or markedly unequal; coherent (into an adaxially split sheath); 1 - adelphous. The staminal tube free from the keel petals. Androecial members 1 -whorled (even though diplostemonous). Androecium exclusively of fertile stamens. Stamens 10; all more or less similar in shape, or distinctly dissimilar in shape; diplostemonous; both opposite and alternating with the corolla members. Anthers separate from one another, or connivent; all alike (and equal, the connective conspicuous); all dorsifixed; 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. Style (in-) curved, or bent (from the base, short). Style glabrous. Stigmatic tissue extrorsely oblique. Carpel 4–25 ovuled (‘4–5’, or ‘numerous’!). Placentation marginal (along the ventral suture). Gynoecium median (the placenta posterior, on the ventral suture). Ovary sessile. Ovules pendulous to ascending; biseriate; arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.

Fruit and seed features. Fruit aerial; stipitate; non-fleshy. The fruiting carpel dehiscent; a legume. Pods somewhat elongated, or much elongated (‘narrowly oblong); not triangular; more or less flat; transversely septate between the seeds, or not transversely septate; wingless (and not ‘margined’). Valves of the dehisced pod not twisted. Fruit 1 celled. Dispersal unit the seed. Seeds endospermic, or non-endospermic; not mucous; compressed, or not compressed; small to medium sized; arillate (the aril rimlike, with a small, tonguelike extension). Cotyledons 2; accumbent. Embryo curved, or bent (the radicle inflexed). Testa non-operculate. Micropyle zigzag, or not zigzag.

Physiology, biochemistry. Aluminium accumulation not found. Photosynthetic pathway: C3.

Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia, South Australia, and Northern Territory. 2n=18. A genus of 2 species; 1 species in Western Australia.

Taxonomic Literature

  • Grieve, B. J.; Blackall, W. E. (1998). How to know Western Australian wildflowers : a key to the flora of the extratropical regions of Western Australia. Part II, Dicotyledons (Amaranthaceae to Lythraceae). University of W.A. Press. Nedlands, W.A.
  • Lee, Alma T. (1973). A new genus of Papilionaceae and related genera.