The families of flowering plants.
Habit and leaf form. Rather small trees, or shrubs; leptocaul (with short- and long-shoots). Leaves deciduous; alternate; petiolate; non-sheathing; simple. Lamina entire; pinnately veined. Leaves exstipulate. Lamina margins serrate, or dentate.
Leaf anatomy. Stomata present; anomocytic.
Lamina dorsiventral. The mesophyll without sclerenchymatous idioblasts; containing calcium oxalate crystals. The mesophyll crystals druses.
Stem anatomy. Cork cambium present; initially deep-seated. Nodes unilacunar (with 7–9 traces). Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with tracheids; with vessels. Vessel end-walls oblique; scalariform, or reticulately perforated. Wood parenchyma apotracheal (in terminal bands). Sieve-tube plastids S-type.
Reproductive type, pollination. Plants hermaphrodite, or andromonoecious. Floral nectaries absent. Pollination anemophilous.
Inflorescence, floral, fruit and seed morphology. Flowers solitary in the axils of 6–12 closely crowded, early season bracts on the short-shoots; bracteate; bracteolate (the lower flowers often having one or two tiny prophylls), or ebracteolate; cyclic. Floral receptacle flattened. Hypogynous disk absent.
Androecium 7–20(–50) (‘more or less many’). Androecial members free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 7–20(–50); filantherous (the filaments short, slender or slightly expanded). Anthers elongate, red, basifixed; non-versatile; dehiscing via longitudinal slits, or dehiscing by longitudinal valves; latrorse; tetrasporangiate; appendaged. The anther appendages apical (by prolongation of the connective). Pollen shed as single grains. Pollen grains aperturate; 3 aperturate, or 5–7 aperturate, or 8–20 aperturate (to ‘many’); colpate, or rugate; 2-celled.
Gynoecium 6–18 carpelled; apocarpous; eu-apocarpous; superior. Carpel incompletely closed; non-stylate (stipitate); with a decurrent stigma, which does not reach the hooded summit because of asymmetric growth of the carpel after anthesis; 1–3(–4) ovuled. Placentation marginal (or submarginal). Ovules anatropous; bitegmic; crassinucellate. Endosperm formation cellular.
Fruit non-fleshy; an aggregate. The fruiting carpel indehiscent; small, samaroid (stipitate, with papery pericarp). Seeds copiously endospermic. Endosperm oily (and proteinaceous). Embryo weakly differentiated (and tiny). Cotyledons 2 (poorly differentiated).
Seedling.Germination phanerocotylar. Seedling cataphylls present (two, but poorly differentiated).
Physiology, biochemistry. Not cyanogenic. Iridoids not detected. Proanthocyanidins present; cyanidin. Ellagic acid absent. Arbutin absent. Saponins/sapogenins present (triterpenoid).
Geography, cytology. Holarctic. Temperate. Assam, China, Japan. 2n = 28.
Taxonomy.Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Trochodendrales. Cronquist’s Subclass Hamamelidae; Hamamelidales. APG 3 core angiosperms; peripheral eudicot; Superorder Ranunculanae; Order Ranunculales.
Species 2. Genera 1; only genus, Euptelea.