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. The leaf lamina dorsiventral. Stomata present; mainly confined to one surface (abaxial); anomocytic. The mesophyll without sclerenchymatous idioblasts; containing crystals. The crystals druses.
Axial (stem, wood) anatomy. Young stems with solid internodes. Pith homogeneous (of relatively thick-walled cells). Cork cambium present; initially deep-seated. Nodes unilacunar (with 79 traces). Internal phloem absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays 1–3 cells wide.
The wood diffuse porous. The vessels small; solitary. The vessel end-walls oblique; scalariform, or reticulately perforated. The vessels without spiral thickening. The axial xylem with tracheids; without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal (in terminal bands). Included phloem absent. The wood not storied.
Reproductive type, pollination. Plants hermaphrodite, or andromonoecious. Floral nectaries absent. Pollination anemophilous.
Inflorescence, floral, fruit and seed morphology. Flowers solitary in the axils of 612 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, phytochemistry. Not cyanogenic. Arbutin absent. Iridoids not detected. Saponins/sapogenins present (triterpenoid). Proanthocyanidins present; cyanidin. Ellagic acid absent. Sieve-tube plastids S-type.
Geography, cytology. Holarctic. Temperate. Assam, China, Japan. 2n = 28.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgrens Superorder Rosiflorae; Trochodendrales. Cronquists Subclass Hamamelidae; Hamamelidales. APG III core angiosperms; peripheral eudicot; Superorder Ranunculanae. APG IV Order Ranunculales.
Species 2. Genera 1; only genus, Euptelea.
Illustrations. • Euptelea pleiosperma, as E. davidiana: Hook. Ic. Pl. 28 (1905). • Euptelea polyandra: Flora Japonica (1870).
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 5th March 2018. delta-intkey.com/angio’.