Pavetta L.

Scientific Description

Family Rubiaceae.

Habit and leaf form. Small trees, or shrubs; deciduous. Leaves well developed (although immature or absent at time of flowering). Plants unarmed. Young stems tetragonal. Helophytic, or mesophytic, or xerophytic. Leaves opposite; membranous, or leathery; petiolate; connate (via the stipules), or not connate; gland-dotted, or not gland-dotted; simple; epulvinate. Leaf blades entire; one-veined, or pinnately veined; cross-venulate. Leaves with stipules. Stipules intrapetiolar; concrescent (connate at base into a small sheath, truncate or with acuminate lobes); with colleters (secreting mucilage), or without colleters; usually caducous, or persistent. Leaf blade margins entire, or serrate. Leaves without a persistent basal meristem. Domatia recorded; represented by pits, or pockets, or hair tufts. Leaf anatomy. Hairs present, or absent. Stem anatomy. Nodes unilacunar, or tri-lacunar. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous, or heterostylous. Entomophilous. Pollination mechanism conspicuously specialized (with passive pollen presentation involving stylar modification), or unspecialized.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in cymes, or in corymbs. The terminal inflorescence unit cymose. Inflorescences terminal. Flowers small, or medium-sized; fragrant; regular; 4 merous; cyclic; tetracyclic. Free hypanthium present, or absent (depending on interpretation); obconic or conic, smooth. Perianth with distinct calyx and corolla; 8; 2 -whorled; the two whorls isomerous. Calyx 4; 1 -whorled; gamosepalous; lobed; hairy, or glabrous; open in bud; tubular; regular; persistent. Corolla 4; 1 -whorled; gamopetalous. Corolla lobes markedly shorter than the tube. Corolla contorted (to the right); cylindrical or salverform; regular; glabrous abaxially, or hairy abaxially (pilose); usually hairy adaxially (pilose at throat), or glabrous adaxially; white. Androecium 4. Androecial members adnate (to the corolla tube); free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 4. Staminal insertion in the throat of the corolla tube. Stamens becoming exserted; isomerous with the perianth; oppositisepalous; filantherous (anthers subsessile). Anthers linear, with large overlapping basal lobes; dorsifixed; reflexed, twisted at anthesis; dehiscing via longitudinal slits; introrse; tetrasporangiate. Pollen shed in aggregates, or shed as single grains; if aggregated, in tetrads. Gynoecium 2 carpelled. The pistil 2 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous; synstylovarious to eu-syncarpous; inferior. Ovary plurilocular; 2 locular. Gynoecium transverse. Epigynous disk present (annular, fleshy). Gynoecium stylate. Styles 1; simple (filiform); attenuate from the ovary, or from a depression at the top of the ovary; apical; shorter than the ovary at anthesis to much longer than the ovary at anthesis; becoming exserted. Stigmas 1; 2 - lobed (inconspicuously bifid); wet type, or dry type; papillate; Group II type and Group IV type. Placentation axile. Ovules 1 per locule (embedded in the succulent placenta); pendulous, or horizontal, or ascending; anatropous, or hemianatropous.

Fruit and seed features. Fruit fleshy; black; indehiscent; a drupe (globose). The drupes with one stone, or with separable pyrenes (then 2 pyrenes). Fruit 2 seeded, or 1 seeded (by abortion). Seeds subglobose or hemispherical; endospermic. Endosperm ruminate, or not ruminate; oily. Seeds winged, or wingless. Cotyledons 2. Embryo curved. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Aluminium accumulation demonstrated, or not found.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, Queensland, and New South Wales. Northern Botanical Province.

Additional characters The genus Pavetta L. is characterised by its corymbiform inflorescences terminal on long peduncle-like leafy or leafless branchlets, connate bracts at the junction of the trichotomously branched inflorescences, and by its white, 4-merous flowers, with long exserted style and fusiform bifid stigma (Reynolds (1993). Corolla lobes spreading (reflexed).

Etymology. After Papat, Indian name of the tree.