Frankenia L.

Scientific Description

Common name. Frankenias. Family Frankeniaceae.

Habit and leaf form. Shrubs, or herbs. Perennial. Leaves cauline (ass.). Stem internodes solid (ass.). Often in saline habitats. Leaves small; opposite (or often crowded on short lateral branches, or often clustered in axils); decussate; petiolate, or sessile; simple; epulvinate. Leaf blades entire; rolled; linear; one-veined. Leaves with stipules (small, stipular leaf uniting pairs of leaves), or without stipules (pairs of leaves joined at base by a ciliated line). Leaf blade margins revolute. Leaves without a persistent basal meristem. Leaf anatomy. Hairs absent (ass.). Extra-floral nectaries absent. Stem anatomy. Secondary thickening developing from a conventional cambial ring, or anomalous; when anomalous, via concentric cambia.

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

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; in spikes, or in heads (globular). The terminal inflorescence unit cymose. Inflorescences axillary; dichasial. Flowers sessile; bracteate (each flower subtended by a pair of opposite bracts); bracteolate (a decussate pair of bracts and bracteoles usually similar and united by a stipular sheath, or bracteoles dissimilar and, or free); regular; cyclic; tetracyclic, or pentacyclic. Perianth with distinct calyx and corolla; 8–14; 2 -whorled; isomerous. Calyx present; 4–6; 1 -whorled; gamosepalous; shortly blunt-lobed; induplicate valvate; tubular (pleated); regular; persistent. Calyx lobes rhombic (usually ciliate). Corolla present; 4–6; 1 -whorled; appendiculate (each petal with a scale at the base of the limb, continued down the sides of the claw); polypetalous; imbricate; regular; white (not usual), or pink, or purple; persistent. Petals linear (and sometimes ribbon-like), or obovate; clawed. Corolla members bilobed, or fringed. Androecial members definite in number. Androecium 4–8. Androecial members free of the perianth; markedly unequal; free of one another, or coherent (shortly united into a ring at base); 1 - adelphous (basally connate); 2 -whorled (usually 3+3). Androecium exclusively of fertile stamens. Stamens 4–8; all more or less similar in shape (ass.); isomerous with the perianth, or diplostemonous to polystemonous; in 2 whorls, hypogynous. Anthers versatile; dehiscing via longitudinal slits; extrorse. Gynoecium (2–)3(–4) carpelled. The pistil 1 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary unilocular; 1 locular. The ‘odd’ carpel posterior. Ovary sessile. Gynoecium stylate. Styles 1; apical. Stigmas (2–)3(–4). Placentation parietal (with (2-)3(-4) placentae). Ovules in the single cavity 1–50 (many); ascending; non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent (splits lengthwise into 2 or 3 valves); a capsule. Capsules loculicidal and valvular (enclosed by the calyx). Fruit 1 celled. Seeds copiously endospermic. Endosperm not oily (starchy). Cotyledons 2. Embryo straight.

Geography, cytology, number of species. World distribution: widespread arid and maritime.

Etymology. After Johann Franke (latinised as Frankenius; 1590–1661), professor of botany and anatomy at Uppsala, who first enumerated the plants of Sweden.