The families of flowering plants
Habit and leaf form. Small trees, or shrubs (with silky young shoots); resinous. Normal plants. Leaves deciduous; alternate; petiolate; simple. Lamina entire; elliptic oblong, or lanceolate; pinnately veined; cross-venulate; cuneate at the base. Leaves exstipulate. Lamina margins entire. Vegetative buds scaly.
Leaf anatomy. The leaf lamina dorsiventral. Stomata present; anomocytic. Hairs present; eglandular and glandular (the former simple, uniseriate, often with bulbous bases, sometimes paired with bases sunken; the latter with biseriate stalks and clavate rather thn capitate); multicellular. Unicellular hairs simple. Lamina with secretory cavities. Secretory cavities containing resin (in the veins, also in the petioles); schizogenous (epithelium-lined). The mesophyll containing crystals. The crystals druses.
Axial (stem, wood) anatomy. Secretory cavities present; with resin (in the pith). Cork cambium present; initially superficial. Nodes tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays narrow (uniseriate, or a few biseriate).
The wood semi-ring porous to diffuse porous. The vessels large; mostly in tangential or oblique rows of up to about 20 members, with a few solitaries. The vessel end-walls more or less horizontal; simple. The vessels without vestured pits; with spiral thickening, or without spiral thickening. The axial xylem without fibre tracheids; with libriform fibres; without septate fibres. The fibres without spiral thickening. The parenchyma scanty paratracheal (to vasicentric and terminal). The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones. Included phloem absent. The wood not storied.
Reproductive type, pollination. Plants dioecious (mostly), or polygamodioecious (occasionally having perfect flowers intermingled with males). Gynoecium of male flowers absent. Pollination anemophilous.
Inflorescence, floral, fruit and seed morphology. Flowers precocious, aggregated in inflorescences; in catkins. The ultimate inflorescence units cymose. Inflorescences axillary; erect, complex catkinlike spikes, each of numerous reduced dichasia; pseudanthial (the staminate flowers interpreted as borne in three-flowered cymules of 14(5) stamens each, the cymules forming clusters of 312(15) stamens which could be taken as single flowers), or not pseudanthial (female inflorescences). Flowers bracteate; ebracteolate, or bracteolate (if the female perianth is interpreted as bracteoles); small (inconspicuous). Free hypanthium absent. Hypogynous disk absent.
Perianth sepaline (female flowers), or absent (in male flowers, and in females if the sepals are interpreted as bracts); of the female flowers (3–)4(–8); of female flowers joined; 1 whorled. Calyx (i.e. the female perianth, alternatively interpretable as bracts or bracteoles) (3–)4(–8); gamosepalous (of minute, unequal and irregularly disposed, glandular-fimbriate scales, more or less connate basally).
Androecium 1–4(–5), or 3–12(–15) (if the theoretical cymules are taken as flowers). Androecial members free of one another. Androecium exclusively of fertile stamens. Stamens 1–4(–5), or 3–12(–15); shortly filantherous. Anthers basifixed; dehiscing via longitudinal slits; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. Anther wall initially with one middle layer. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 3–6 aperturate; colporate; 2-celled.
Gynoecium 1 carpelled (ostensibly), or 2 carpelled (theoretically, on the evidence of teratological flowers with bilocular ovaries and two styles). The pistil 1 celled. Gynoecium (pseudo) monomerous, or syncarpous (depending on interpretation); of one carpel (ostensibly), or eu-syncarpous (if considered pseudomonomeric); superior. Carpel (if viewed as monomeric) stylate (with a linear, distally expanded style and decurrent stigma, the stigmatic groove and the placenta turned away from the axis and towards the subtending bract); 1 ovuled. Ovary if viewed as pseudomonomeric, 1 locular; sessile. Gynoecium stylate. Styles 1 (slender, curved, caducous); apical. Stigmas 1 (decurrent). Placentation parietal (the ovule attached to the side of the ovary). Ovules in the single cavity 1; ascending; anatropous to amphitropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids broadly triangular. Endosperm formation nuclear. Embryogeny of no clear type.
Fruit fleshy to non-fleshy. The fruiting carpel indehiscent; drupaceous. Fruit (if considered syncarpous, indehiscent; a drupe (a slightly asymmetric, somewhat flattened, dry drupe, with a conspicuously reticulate endocarp). The drupes with one stone. Fruit 1 seeded. Seeds thinly endospermic. Endosperm starchy. Seeds with starch. Embryo well differentiated. Cotyledons 2. Embryo straight (linear).
Physiology, phytochemistry. Not cyanogenic. Sieve-tube plastids S-type.
Geography, cytology. Holarctic and Neotropical. Sub-tropical. Southeast U.S.A. 2n = 32.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgrens Superorder Rutiflorae; Sapindales. Cronquists Subclass Hamamelidae; Leitneriales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Sapindales (as a synonym of Simaroubaceae).
Species 1. Genera 1; only genus, Leitneria.
General remarks. In addition to characters relying on limited sampling (leaf and wood anatomy, anther wall ontogeny), these compiled descriptions have Leitneria differing from (most?) Simaroubaceae (q.v.) in the unicellular gynoecium with apical style, as well as in the ascending ovules with long outer integument, and endospermic seeds.
Illustrations. • Leitneria floridana: Hook. Ic. Pl. 11 (1867–71).
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: 30th September 2017. delta-intkey.com/angio’.