Habit and leaf form. Small shrubs, or herbs. ‘Normal’ plants, or plants of very peculiar form (often reduced to a single annual pair of leaves, some forms partly subterranean with only a clear window at each leaf tip exposed above-ground). Plants succulent. The herbs annual, or perennial. Leaves cauline. Plants with neither basal nor terminal concentrations of leaves. Young stems cylindrical to oval in section (branchlets terete or compressed). Stem internodes solid. To up to 1 m high (or prostrate). Xerophytic. Leaves minute to medium-sized; opposite; fleshy; imbricate to not imbricate; petiolate to sessile (leaves gradually tapering to a broad petiole); connate, or not connate; simple; epulvinate. Leaf blades entire; flat, or solid; ovate, or obovate, or linear. Leaf blade margins entire. Vegetative buds not scaly. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present, or absent. Urticating hairs absent. Stem anatomy. Secondary thickening absent, or anomalous; via concentric cambia (in the woodier genera,), or from a single cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous (diurnal).
Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; (when aggregated) in cymes. The terminal inflorescence unit (when flowers aggregated) cymose. Inflorescences cymes and heads. Flowers pedicellate (A), or sessile (A); ebracteate; ebracteolate; small, or medium-sized; regular; cyclic; pentacyclic to polycyclic. Free hypanthium present; incorporating calyx and stamens. Hypogynous disk present, or absent. Perianth sepaline; 4. Calyx present; 4; 1 -whorled; polysepalous, or gamosepalous (fused for up to half of length); blunt-lobed; saccate; unequal but not bilabiate, or regular (segments equal in length or the opposite pair longer, apex cuspidate); green (outside), or white (inside), or green and yellow, or green and pink; fleshy; persistent. Corolla absent. Androecial members definite in number, or indefinite in number. Androecium (3–)4–5, or 8–10, or 15–200 (i.e. to ‘many’, by branching). Androecial members branched, or unbranched. Androecial sequence determinable, or not determinable. Androecial members when branched/many, maturing centrifugally; all equal; coherent; 4 - adelphous (in groups alternating with the perianth segments); 1–16 -whorled (i.e to ‘many whorls’). Androecium exclusively of fertile stamens (? — i.e. no staminodal ‘petals’). Stamens 4–120 (i.e. to ‘many’); isomerous with the perianth to polystemonous; filantherous. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Pollen shed as single grains. Gynoecium 4 carpelled. The pistil 4 celled. Gynoecium syncarpous; synovarious to synstylovarious; superior. Ovary plurilocular; 4 locular; sessile. Gynoecium stylate. Styles 4. Stigmas 4. Placentation axile, or basal to axile. Ovules 20–50 per locule (to many); arillate, or non-arillate; anatropous, or campylotropous.
Fruit and seed features. Fruit non-fleshy; dehiscent (dehisces when wet); a capsule. Capsules septicidal, or septicidal and loculicidal. Fruit 4 celled; 20–100 seeded (many). Seeds non-endospermic. Perisperm present (mealy). Embryo well differentiated. Cotyledons 2. Embryo curved.
Etymology. From genus Gunnia and the Greek for appearance, meaning that the genus looks like the genus Gunnia.