Levenhookia R.Br.

Scientific Description

Family Stylidiaceae.

Habit and leaf form. Small, erect herbs. Annual (ephemeral); plants with neither basal nor terminal concentrations of leaves; rhizomatous, or tuberous. Helophytic (in bogs), or mesophytic to xerophytic. Leaves alternate; spiral; ‘herbaceous’, or leathery; imbricate; subsessile; sheathing; simple. Leaf blades entire; parallel-veined; without cross-venules. Leaves without stipules. Stem anatomy. Secondary thickening anomalous; from a single cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous. Pollination mechanism conspicuously specialized (when the flower is visited by an insect the labellum is released and its movement causes the column to shed the pollen).

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’. Inflorescence few-flowered, or many-flowered. Flowers in racemes, or in umbels. The terminal inflorescence unit cymose, or racemose. Inflorescences scapiflorous, or not scapiflorous; terminal; simple or corymbosely branched. Flowers bracteate; small to medium-sized; very irregular; resupinate, or not resupinate. The floral asymmetry involving the perianth and involving the androecium. Flowers 5 merous; cyclic; pentacyclic. Floral receptacle developing an androphore (the peculiar ‘stylar column’, which bears the stigma and the anthers at its tip, sometimes being thus interpreted), or with neither androphore nor gynophore (if the column is interpreted as a gynostemium). Free hypanthium present. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; gamosepalous (tube globular, lobes all free); imbricate; with the median member posterior. Corolla 5; 1 -whorled; gamopetalous; imbricate; unequal but not bilabiate; white, or pink. Androecium 2. Androecial members free of the perianth; united with the gynoecium (seemingly forming a column with the style, the stigma and stamens borne at the tip of the column); coherent; 1 - adelphous (via the gynostemium); 1 -whorled (posterior-lateral). Androecium exclusively of fertile stamens. Stamens 2; reduced in number relative to the adjacent perianth. Anthers dehiscing via longitudinal slits; extrorse; tetrasporangiate. Gynoecium 2 carpelled. The pistil 1 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous (pseudomonomerous); eu-syncarpous; inferior. Ovary unilocular; 1 locular (by abortion of the posterior locule). Gynoecium median. Epigynous disk present, or absent. Styles 1. Stigmas 2 - lobed; long, hairy, finger-like projections; dry type; papillate; Group II type. Placentation basal. Ovules in the single cavity 1, or 4; pendulous, or horizontal, or ascending; anatropous.

Fruit and seed features. Fruit fleshy, or non-fleshy; dehiscent; a capsule; 1–4 seeded (i.e. ‘few’). Seeds endospermic. Endosperm oily. Seeds minute. Cotyledons 2. Seedling. Germination phanerocotylar.

Physiology, biochemistry. Aluminium accumulation not found.

Geography, cytology, number of species. Native of Australia. Australian states and territories: Western Australia, South Australia, New South Wales, Victoria, Australian Capital Territory, and Tasmania. South-West Botanical Province.

Additional characters Perianth of 5 similar members and the median inner member modified into the labellum (the 4 almost rounded lobes each tapered at the base). Column erect, immobile, slightly exserted. Labellum motile (irritable, concave, hood shaped but often with broad lobes at the base, enclosing the top of the column and either sessile on the margin of the corolla tube or stipitate).