The families of flowering plants.
IncludingNuculaceae Lam. & DC., Platycaryaceae Nakai, Pterocaryaceae Nak.Excluding Rhoipteleaceae
Habit and leaf form. Trees (mostly), or shrubs (a few); often resinous; leptocaul. Leaves deciduous; alternate (mostly), or opposite (Alfaroa, Oreomunnia); petiolate, or sessile; non-sheathing; aromatic (with aromatic, resinous, peltate gland scales, and often with other types of glands in addition); compound; (impari-) pinnate, or ternate. Lamina pinnately veined; cross-venulate. Leaves exstipulate. Vegetative buds brown-hairy, scaly, or not scaly (the buds commonly several, superposed). Leaves without a persistent basal meristem. Domatia occurring in the family (4 genera); manifested as pits, or pockets, or hair tufts.
Leaf anatomy. Stomata present; anomocytic.
The mesophyll containing calcium oxalate crystals. The mesophyll crystals druses. Minor leaf veins without phloem transfer cells (Juglans).
Stem anatomy. Secretory cavities absent (but often with scattered secretory cells). Cork cambium present; initially superficial. Nodes tri-lacunar, or multilacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with tracheids, or without tracheids; with fibre tracheids, or without fibre tracheids; with vessels. Vessel end-walls scalariform, or simple. Vessels without vestured pits. Wood parenchyma typically apotracheal, or apotracheal and paratracheal (often with a little paratracheal in addition). Sieve-tube plastids S-type. Pith with diaphragms, or without diaphragms.
Reproductive type, pollination. Plants monoecious (usually), or dioecious (occasionally). Gynoecium of male flowers vestigial, or absent. Pollination anemophilous.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (mostly), or solitary (female flowers sometimes solitary); in catkins (mostly, these usually drooping, sometimes erect, sometimes grouped into terminal panicles), or in racemes (female, sometimes), or in spikes (female, sometimes). Inflorescences mostly in the form of catkins, which may themselves be grouped into terminal panicles; the catkins unisexual, or bisexual with proximal staminate and distal pistillate flowers; female flowers rarely solitary, or in spikes or racemes. Flowers bracteate; two bracteolate, or ebracteolate (the bractlets often adnate to the sepals (male) or to the bract (female), in the latter case often forming a cupulate involucre maturing to form a husk around the fruit); flowers individually small (and inconspicuous).
Perianthsepaline, or vestigial, or absent; when present, (1–)4(–5). Calyx when present, (1–)4(–5); more or less adnate with the bracteoles or obsolete in male flowers, consisting of four calyx teeth or suppressed in female flowers.
Androecium in male flowers, (3–)5–50(–100) (or more — decreasing in number acropetally in the catkin). Androecial members free of the perianth; free of one another. Androecium in male flowers, exclusively of fertile stamens. Stamens (3–)5–50(–100) (or more); diplostemonous to polystemonous; shortly filantherous. Anthers basifixed; dehiscing via longitudinal slits; tetrasporangiate. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Anther wall initially with more than one middle layer. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 3–9(–16) aperturate; porate (3–7), or foraminate to rugate (6–16, Juglans); 2-celled.
Gynoecium 2(–3) carpelled. The pistil 1–8 celled. Gynoecium syncarpous; synovarious to synstylovarious; inferior. Ovary 1 locular (above), or 2(–3) locular (below, usually, but the partitioning falling short of the apex, and sometimes 4–8 celled below, by ‘false’ partitions). Locules secondarily divided by ‘false septa’, or without ‘false septa’. Gynoecium median, or transverse. Epigynous disk absent. Gynoecium shortly stylate, or non-stylate. Styles 1–2; free to partially joined; apical. Stigmas 2; dry type; non-papillate; Group II type. Placentation basal (the ovule borne on top of the partition). Ovules in the single cavity 1; ascending; non-arillate; orthotropous; unitegmic; crassinucellate. Embryo-sac development Polygonum-type. Antipodal cells formed; 3; not proliferating; ephemeral. Endosperm formation nuclear. Embryogeny asterad.
Fruit fleshy, or non-fleshy; indehiscent; a drupe (the softer husk sometimes splitting to release the bony pericarp), or a nut, or a samara. The drupes with one stone. Fruit 1 seeded. Seeds non-endospermic. Embryo well differentiated (large, oily). Cotyledons 2 (often massive, deeply lobed from the false septa, and sculptured). Embryo achlorophyllous (2/4).
Seedling.Germination phanerocotylar, or cryptocotylar.
Physiology, biochemistry. Cyanogenic, or not cyanogenic. Alkaloids absent (10 species). Iridoids not detected. Proanthocyanidins present, or absent; delphinidin, or cyanidin and delphinidin. Flavonols present, or absent (Pterocarya); quercetin and myricetin (Juglans). Ellagic acid present (Pterocarya), or absent (Juglans). Arbutin absent. Aluminium accumulation demonstrated (rarely), or not found (usually). Sugars transported as sugar alcohols + oligosaccharides + sucrose (from 9 species and three genera). C3. C3 physiology recorded directly in Juglans.
Geography, cytology. Holarctic, Paleotropical, and Neotropical. Temperate to tropical. Basically North temperate and subtropical, extending to India, Indochina, Malaysia and Andean South America - absent from Africa and Australia. X = 16.
Taxonomy.Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Juglandales. Cronquist’s Subclass Hamamelidae; Juglandales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Fagales.
Species 50. Genera 8; Alfaroa, Carya, Cyclocarya, Engelhardtia,Juglans, Oreomunnia, Platycarya, Pterocarya.
Economic uses, etc. Valuable sources of edible nuts (walnut, pecan), and many valuable timber species (walnuts, hickory).