Habit and leaf form. Herbs. Annual. Young stems tetragonal. Helophytic to xerophytic. Leaves opposite; usually decussate, or not decussate; subsessile, or sessile; gland-dotted, or not gland-dotted; simple. Leaf blades entire; elliptic, or oblong, or ovate, or obovate, or linear; pinnately veined; cross-venulate; auriculate at the base, or cordate (or attenuate). Leaves without stipules. Leaf blade margins entire. Leaves without a persistent basal meristem. Stem anatomy. Secondary thickening developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous, or heterostylous. Entomophilous.
Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, or in heads, or in umbels, or in fascicles (or clusters). The terminal inflorescence unit cymose, or racemose. Inflorescences axillary. Flowers pedicellate; bracteolate; minute to medium-sized; regular; 4 merous; pentacyclic. Floral receptacle developing an androphore, or with neither androphore nor gynophore. Free hypanthium present; usually campanulate, or urceolate; usually faintly 8-ribbed and glabrous; sinus appendages present or absent. Hypogynous disk present, or absent. Perianth with distinct calyx and corolla; (3–)8–16(–32); 2 -whorled; isomerous. Calyx present; 4; 1 -whorled; gamosepalous; blunt-lobed; lobes valvate; tubular, or campanulate, or urceolate; unequal but not bilabiate, or regular; persistent. Epicalyx present, or absent. Corolla present, or absent; 4; 1 -whorled; polypetalous; plicate; unequal but not bilabiate, or regular; white, or red, or pink, or purple. Petals elliptic, or obovate, or orbicular; sessile. Androecial members definite in number. Androecium 4–8. Androecial sequence determinable, or not determinable. Androecial members free of the perianth; all equal; free of one another; 1–3 -whorled (or several). Androecium exclusively of fertile stamens. Stamens 4–8; attached inside the hypanthium; all more or less similar in shape; reduced in number relative to the adjacent perianth to isomerous with the perianth to polystemonous; alternisepalous, or oppositisepalous; inflexed in bud, or erect in bud. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Gynoecium 2–4(–6) carpelled. The pistil (1–)2–4 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary unilocular, or plurilocular; (1–)2–4 locular; sessile to stipitate. Gynoecium stylate. Styles 1; apical. Stigmas 1; capitate. Placentation rarely (i.e.when unilocular), parietal; axile. Ovules (1–)5–50 per locule; ascending, or horizontal; non-arillate; anatropous.
Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules splitting irregularly to circumscissile, or septicidal to valvular. Seeds non-endospermic; wingless. Cotyledons 2. Embryo straight.
Etymology. After Johannes Ammann (1797–42), German professor of botany at Leningrad (then St Petersburg); or (less likely) Paul Ammann (1634–91), professor at Leipzig.
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Western Australian Herbarium (1998–). FloraBase—the Western Australian Flora. Department of Biodiversity, Conservation and Attractions. https://florabase.dpaw.wa.gov.au/