Pisonia L.

Scientific Description

Family Nyctaginaceae.

Habit and leaf form. Trees, or shrubs, or lianas. Leaves cauline. Stem internodes solid. Mesophytic. Leaves alternate, or opposite (usually, sometimes crowded towards end of twig); petiolate; non-sheathing; simple. Leaf blades entire; elliptic (broadly), or ovate (broadly); pinnately veined; cross-venulate; attenuate at the base. Leaves without stipules. Leaf blade margins entire. Leaf anatomy. Hairs present (mostly glabrescent); glandular hairs present. Extra-floral nectaries absent. Stem anatomy. Secondary thickening anomalous; via concentric cambia.

Reproductive type, pollination. Fertile flowers hermaphrodite, or functionally male and functionally female, or functionally male, or functionally female. Unisexual flowers present, or absent. Plants hermaphrodite, or monoecious, or dioecious. Female flowers without staminodes. Male flowers with pistillodes, or without pistillodes.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in cymes (cymes often in terminal panicles,each ultimate branch with 1–3 flowers). The terminal inflorescence unit cymose. Inflorescences terminal, or axillary; cyme expands in fruit; with involucral bracts, or without involucral bracts; pseudanthial, or not pseudanthial. Flowers sessile; bracteate (AKB), or ebracteate (small, caducous). Bracts deciduous. Flowers bracteolate (KB), or ebracteolate (small, caducous). Bracteoles deciduous. Flowers small, or medium-sized; regular; cyclic; tricyclic. Free hypanthium absent. Perianth sepaline; 5(–10); 1 -whorled; joined. Calyx present; 5 (usually); 1 -whorled; gamosepalous; blunt-lobed; valvate, or plicate in bud; campanulate (male or female), or funnel-shaped (male), or urceolate (female), or tubular (female), or or bisexual and contracted above the ovary; regular; cream, or yellow; base persistent. Corolla absent. Fertile stamens present, or absent (female flowers). Androecial members definite in number. Androecium 2–20. Androecial sequence determinable, or not determinable. Androecial members when many, maturing centrifugally; adnate (to the perianth tube), or free of the perianth; markedly unequal; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens (2–)6–8(–20); all more or less similar in shape; hypogonous; inflexed in bud. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Fertile gynoecium present, or absent (male flowers). 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, or with a lateral style; 1 ovuled. Placentation basal. Ovary stipitate (shortly stipitate). Stigmas lobed. Ovules ascending; non-arillate; campylotropous, or hemianatropous.

Fruit and seed features. Fruit non-fleshy. The fruiting carpel indehiscent; an achene, or nucular. Fruit 1 celled; 1 seeded. Seeds endospermic, or non-endospermic. Perisperm present. Embryo well differentiated (large). Cotyledons 2. Embryo curved, or straight, or bent.

Etymology. In honour of the Dutch doctor Willem Piso (active 1648), who wrote a book about medicinal plants from Brazil.