Limnanthaceae R. Br.
Habit and leaf form. Small, weak marsh herbs; non-laticiferous and without coloured juice. Plants (sub) succulent. Annual. Helophytic. Leaves alternate; petiolate; simple, or compound; when compound, pinnate, or bipinnate. Lamina when simple, dissected; pinnatifid, or much-divided; pinnately veined. Leaves exstipulate.
Leaf anatomy. Hydathodes commonly present. Stomata present; on both surfaces (more numerous below); anomocytic.
Lamina dorsiventral. Minor leaf veins without phloem transfer cells (Limnanthes).
Stem anatomy. Primary vascular tissue comprising a ring of bundles. Secondary thickening absent. Vessels without vestured pits.
Reproductive type, pollination. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the androecium (from glands internal and adnate to the antesepalous stamens).
Inflorescence, floral, fruit and seed morphology. Flowers solitary; axillary (on long pedicels); ebracteate; ebracteolate; regular; (4–)5 merous (Limnanthes), or 3 merous (Floerkea); cyclic; tetracyclic, or pentacyclic. Free hypanthium present. Hypogynous disk absent.
Perianth with distinct calyx and corolla; 6–10; 2 whorled; isomerous. Calyx (4–)5 (Limnanthes), or 3 (Floerkea); 1 whorled; polysepalous, or gamosepalous (no more than slightly so). Calyx lobes markedly longer than the tube. Calyx regular; slightly imbricate (Floerkea), or valvate (Limnanthes). Corolla (4–)5, or 3; 1 whorled; polypetalous; contorted; persistent.
Androecium 3 (sometimes, in Floerkea), or 6, or 8, or 10 (persistent). Androecial members free of the perianth; free of one another; 1 whorled (sometimes, in Floerkea), or 2 whorled. Androecium exclusively of fertile stamens. Stamens 3, or 6, or 8, or 10; isomerous with the perianth (sometimes, in Floerkea), or diplostemonous (usually); oppositisepalous; filantherous (the antesepalous members with an internal, adnate nectariferous gland). Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with more than one middle layer (2). Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 2–4 aperturate; colpate (syncolpate), or colporate; 2-celled.
Gynoecium opposite the sepals, (4–)5 carpelled (Limnanthes), or 2–3 carpelled (Floerkea). Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil when considered syncarpous, (2–)3–5 celled. Gynoecium apocarpous (almost), or syncarpous; synstylovarious to eu-syncarpous, or synstylous (very deeply lobed, the almost-separate carpels united by the style, becoming free when ripe); superior to partly inferior (the petals and stamens slightly perigynous). Carpel 1 ovuled. Placentation basal. Ovary if treated as syncarpous, (2–)3–5 locular (but deeply lobed). Gynoecium stylate. Styles 1 (but sometimes more or less deeply cleft); from a depression at the top of the ovary; ‘gynobasic’. Stigmas (2–)3–5; dry type; papillate. Placentation basal. Ovules 1 per locule; ascending; apotropous (the micropyle facing outwards and downwards); with ventral raphe; anatropous; unitegmic; tenuinucellate. Embryo-sac development Drusa-type (with unusual ontogeny, tetrasporic, 4-nucleate in Limnanthes, 6-nucleate in Floerkea). Synergids hooked (large, with or without filiform apparatus). Endosperm formation nuclear. Endosperm haustoria at least sometimes present; lateral (in Floerkea). Embryogeny onagrad.
Fruit non-fleshy; more or less an aggregate, or not an aggregate (if interpreted as syncarpous); interpreted as syncarpous, a schizocarp. Mericarps (2–)3–5; comprising nutlets. Dispersal unit the mericarp. Seeds non-endospermic; with amyloid. Embryo well differentiated. Cotyledons 2 (large); fleshy, cordate. Embryo chlorophyllous; straight.
Seedling. Germination phanerocotylar.
Physiology, biochemistry. Mustard-oils present. Not cyanogenic. Proanthocyanidins present; cyanidin and delphinidin. Flavonols present; kaempferol, quercetin, and myricetin. Saponins/sapogenins absent.
Geography, cytology. Holarctic. Temperate. Temperate North America. X = 5.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Violiflorae; Capparales (re-assigned here, cf. Gadek et al. 1992). Cronquist’s Subclass Rosidae; Geraniales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Brassicales.
Species 11. Genera 2; Floerkea, Limnanthes.
• Technical details: Limnanthes, Floerkea.
• Limnanthes douglasii: Bot. Reg. 1673, 1835.