Lythraceae Jaume St.-Hil.
Including Ammanniaceae Horan., Diplodontaceae Dulac, Lagerstroemiaceae J.G. Agardh, Lawsoniaceae J.G. Agardh, Salicariaceae Juss.
Habit and leaf form. Herbs (mostly), or shrubs, or trees. Plants non-succulent. Helophytic to xerophytic, or hydrophytic (in Rotala); rooted. Leaves opposite (usually), or alternate, or whorled; when alternate, spiral; petiolate to sessile; gland-dotted, or not gland-dotted; simple. Lamina entire; pinnately veined; cross-venulate. Leaves stipulate (the stipules small), or exstipulate. Lamina margins entire. Leaves without a persistent basal meristem.
Leaf anatomy. Mucilaginous epidermis present, or absent.
Lamina dorsiventral (usually), or isobilateral (rarely). The mesophyll without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Cuphea, Lythrum).
Stem anatomy. Young stems cylindrical, or tetragonal. Cork cambium present; initially deep-seated. Nodes unilacunar (usually), or tri-lacunar. Primary vascular tissue bicollateral. Internal phloem present. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids (Heimia, Woodfordia, Pleurophora), or without fibre tracheids (mostly); with vessels. Vessel end-walls simple. Vessels with vestured pits. Wood parenchyma predominantly paratracheal.
Reproductive type, pollination. Plants hermaphrodite; homostylous (mostly), or heterostylous (several genera, e.g. Pemphis, Adenaria). Pollination entomophilous.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, in panicles, in racemes, and in verticils. The ultimate inflorescence unit cymose, or racemose. Inflorescences terminal, or axillary. Flowers two bracteolate; minute to medium-sized; regular to very irregular. The floral irregularity when apparent, involving the perianth and involving the androecium. Flowers usually 4 merous, or 6 merous; cyclic, or partially acyclic. When partially non-cyclic, the androecium acyclic. Flowers when fully cyclic, usually pentacyclic. Floral receptacle developing an androphore, or with neither androphore nor gynophore. Free hypanthium present (this elongated, sometimes with a posterior spur). Hypogynous disk or a unilateral gland (Cuphea) present (around G), or absent.
Perianth with distinct calyx and corolla (usually), or sepaline (C rarely absent); (3–)8–16(–32); 2 whorled (usually), or 1 whorled; isomerous. Calyx (3–)4, or 6, or 8(–16); 1 whorled; polysepalous (sometimes?), or gamosepalous (usually, in that the ‘floral tube’ extends beyond the level of insertion of the corolla); tubular, or campanulate, or urceolate (rarely); unequal but not bilabiate, or regular; persistent; lobes valvate. Epicalyx present (commonly), or absent. Corolla (3–)4, or 6, or 8(–16); 1 whorled; polypetalous (at the mouth of the hypanthium); plicate; unequal but not bilabiate, or regular; often red, or purple, or orange. Petals clawed, or sessile.
Androecium (4–)8–16(–100) (rarely fewer than K, usually twice K or C, sometimes ‘many’). Androecial members when numerous, maturing centripetally (or the outer cycle initiating first); adnate (to the hypanthium, low down); all equal, or markedly unequal; free of one another; 1–3 whorled (or several). Androecium usually exclusively of fertile stamens. Stamens (4–)8–16(–35); reduced in number relative to the adjacent perianth to isomerous with the perianth to polystemonous; alternisepalous, or oppositisepalous; inflexed in bud (usually), or erect in bud. Anthers dorsifixed; versatile (mostly), or non-versatile (Crenea, Pleurophora); dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with more than one middle layer; of the ‘dicot’ type. Tapetum glandular. Pollen grains aperturate; 3 aperturate (usually), or 9 aperturate; colpate, or colporate, or colpate and colporate (sometimes with pseudocolpi intervening, sometimes syncolpate); 2-celled (in 6 genera).
Gynoecium 2–4(–6) carpelled. The pistil 1 celled, or 2–4(–6) celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 1 locular (rarely), or 2–4(–6) locular (but sometimes with the septa not reaching the top); sessile to stipitate (stipitate in Lagerstroemia, Diplusodon, Peplis etc.). Gynoecium stylate (mostly), or non-stylate to stylate. Styles 1; apical. Stigmas 1; usually capitate; wet type (known only in Lagerstroemia), or dry type (recorded in 13 genera); papillate; Group II type. Placentation rarely (i.e.when unilocular), parietal; usually axile. Ovules (1–)5–50 per locule (usually ‘many’); ascending, or horizontal; non-arillate; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids hooked. Hypostase usually present. Endosperm formation nuclear. Embryogeny onagrad.
Fruit non-fleshy; dehiscent, or indehiscent; a capsule, or capsular-indehiscent. Capsules septicidal, or loculicidal, or circumscissile, or splitting irregularly. Seeds non-endospermic; winged (in a few genera, the wing unilateral in Lagerstroemia, encircling in Lafoensia, Galpinia etc.), or wingless (in most genera). Cotyledons 2; flat (usually), or folded (Lagerstroemia). Embryo achlorophyllous (2/3); straight.
Seedling. Germination phanerocotylar.
Physiology, biochemistry. Not cyanogenic. Alkaloids present, or absent (mostly). Iridoids not detected. Arthroquinones detected (Woodfordia); polyacetate derived. Proanthocyanidins absent. Flavonols present (Cuphea), or absent; when present, kaempferol and quercetin. Ellagic acid present (4 species, 4 genera). Saponins/sapogenins absent. Aluminium accumulation not found. Sugars transported as oligosaccharides + sucrose (Lagerstroemia). C3. C3 physiology recorded directly in Ammannia, Lythrum. Anatomy non-C4 type (Decodon).
Geography, cytology. Temperate to tropical. Cosmopolitan, except frigid regions. X = 5–11.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Myrtiflorae; Myrtales. Cronquist’s Subclass Rosidae; Myrtales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Myrtales.
Species 580. Genera 28; Adenaria, Ammannia, Capuronia, Crenea, Cuphea, Decodon, Didiplis, Diplusodon, Galpinia, Ginoria, Haitia, Heimia, Hionanthera, Koehneria, Lafoensia, Lagerstroemia, Lawsonia, Lourtella, Lythrum, Nesaea, Pehria, Pemphis, Peplis, Physocalymma, Pleurophora, Rotala, Tetrataxis, Woodfordia.
• Technical details: Lythrum.
• Technical details: Lythrum (Lindley).
• Technical details: Nesaea (Thonner).
• Cuphea llavea: Bot. Reg. 1386, 1830.
• Heimia salicifolia var. grandiflora: Bot. Reg. 60, 1841.
• Lythrum salicaria (B. Ent.).