The families of flowering plants.
IncludingAesculaceae Lindl., Aesculaceae Berchtold & Presl, Castanaceae Link, Paviaceae Horan.
Habit and leaf form. Trees and shrubs. Mesophytic. Leaves deciduous; medium-sized, or large; opposite; petiolate; compound; palmate (3–11 foliolate). Lamina palmately veined; cross-venulate. Leaves exstipulate. Lamina margins (of the leaflets) crenate, or serrate. Vegetative buds scaly (and usually sticky). Domatia occurring in the family; manifested as hair tufts.
Leaf anatomy. Lamina dorsiventral. Minor leaf veins with phloem transfer cells (Aesculus).
Stem anatomy. Cork cambium present. Nodes tri-lacunar, or multilacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with libriform fibres; with vessels. Vessel end-walls simple, or scalariform and simple. Vessels without vestured pits. Wood ring porous; partially storied (VP, VPR); parenchyma apotracheal and paratracheal.
Reproductive type, pollination. Plants andromonoecious (usually, the upper, first-opening flowers male), or hermaphrodite, or polygamomonoecious (some flowers effectively female, by shedding of immature stamens). Gynoecium of male flowers vestigial. Pollination entomophilous; via hymenoptera (bees).
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’. The ultimate inflorescence unit cymose. Inflorescences terminal; large racemes of cincinni. Flowers medium-sized to large; very irregular; zygomorphic. The floral irregularity involving the perianth, or involving the perianth and involving the androecium (and often also the disk). Flowers cyclic; tetracyclic to pentacyclic. Free hypanthium absent. Hypogynous disk present; extrastaminal; annular (or unilateral).
Perianthwith distinct calyx and corolla; (9–)10; 2 whorled; isomerous, or anisomerous. Calyx 5; 1 whorled; almost polysepalous (Billia), or gamosepalous (Aesculus); when gamosepalous, blunt-lobed; campanulate, or tubular; unequal but not bilabiate, or regular; imbricate. Corolla (4–)5 (the middle of the lower three members sometimes missing); 1 whorled; polypetalous; imbricate; unequal but not bilabiate; with contrasting markings (with yellow spots, which later turn red). Petals clawed.
Androecium (5–)6–8 (the inner whorl of five complete, the outer more or less reduced). Androecial members free of the perianth; markedly unequal; free of one another; 2 whorled. Androecium exclusively of fertile stamens. Stamens (5–)6–8; reduced in number relative to the adjacent perianth to isomerous with the perianth; alternisepalous, or oppositisepalous. Anthers dorsifixed (near the base); versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Microsporogenesis simultaneous. Tapetum glandular. Pollen grains aperturate; 3 aperturate; colporate; 2-celled.
Gynoecium (2–)3(–4) carpelled. Carpels reduced in number relative to the perianth. The pistil (2–)3(–4) celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary (2–)3(–4) locular. The ‘odd’ carpel anterior. Ovary sessile. Gynoecium stylate. Styles 1; attenuate from the ovary; apical. Stigmas 1; 1 lobed, or (2–)3(–4) lobed; dry type; papillate; Group II type (B(i)). Placentation axile. Ovules 2 per locule; pendulous to ascending (sometimes the lower ascending, the upper pendulous); when not orthotropous, apotropous (Engler); superposed; non-arillate; anatropous, or amphitropous, or orthotropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type (?). Endosperm formation nuclear.
Fruit non-fleshy; dehiscent; a capsule (smooth to echinate). Capsules loculicidal (large, leathery, often one-loculed by abortion). Fruit 1 seeded (often, by abortion), or 2–5 seeded. Seeds non-endospermic; large (with a large hilum reflecting incorporation of the funicle in the placenta, and adnation of the placental obturator). Embryo well differentiated. Cotyledons 2; thick and fleshy, often with one much larger than the other, often adherent face to face.Embryo chlorophyllous (1/1); curved.
Physiology, biochemistry. Not cyanogenic. Iridoids not detected. Proanthocyanidins present; cyanidin. Flavonols present; kaempferol, or kaempferol and quercetin. Ellagic acid absent (Aesculus). Arbutin absent. Saponins/sapogenins present, or absent. Aluminium accumulation not found. Sugars transported as sucrose. C3. C3 physiology recorded directly in Aesculus.
Geography, cytology. Holarctic, Paleotropical, and Neotropical. Temperate to tropical. North temperate and Central and South America. X = 20.
Taxonomy.Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Sapindales. Cronquist’s Subclass Rosidae; Sapindales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Sapindales (as a synonym of Sapindaceae).
Species 15. Genera 2; Aesculus, Billia.
Economic uses, etc. Some cultivated ornamentals, notable horse-chestnut (Aesculus hippocastanum) which is widely planted in temperate regions.
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