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The families of flowering plants

L. Watson and M.J. Dallwitz

Physenaceae Takhtajan

Habit and leaf form. Small trees, or shrubs. Leaves alternate; petiolate; non-sheathing; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire; flat.

Leaf anatomy. The leaf lamina dorsiventral. Mucilaginous epidermis absent. Stomata mainly confined to one surface (abaxial); anomocytic. Hairs absent. Adaxial hypodermis absent. The mesophyll containing crystals. The crystals druses.

Axial (stem, wood) anatomy. Cork cambium present; initially superficial (subepidermal). Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles. Secondary thickening developing from a conventional cambial ring.

The wood diffuse porous. The vessel end-walls more or less horizontal; simple. The vessels without vestured pits. The axial xylem with tracheids; without fibre tracheids (the pits no more than slightly bordered); with libriform fibres. The parenchyma paratracheal (aliform, or confluent and unilateral); wood not storied.

Reproductive type, pollination. Plants dioecious. Female flowers without staminodes. Gynoecium of male flowers pistillodial to vestigial. Pollination anemophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; (male and female) in racemes. The ultimate inflorescence units racemose. Inflorescences axillary; axillary racemes. Flowers small to medium-sized; regular. Floral receptacle with neither androphore nor gynophore. Free hypanthium absent. Hypogynous disk absent.

Perianth sepaline; 5–9; 1 whorled. Calyx 5–9 (the sepals internally hairy, with multicellular, unbranched hairs); 1 whorled; more or less polysepalous, or partially gamosepalous, or gamosepalous (some members slightly united below); blunt-lobed, or toothed; regular; persistent; non-accrescent; weakly imbricate.

Androecium in male flowers, (8–)10–14(–25). Androecial members free of the perianth; more or less coherent (the filaments of a variable number being united at the base), or free of one another; 1–2 whorled (the members arising as one whorl, but one or more members may be positioned outside the cycle). Androecium exclusively of fertile stamens. Stamens (8–)10–14(–25); isomerous with the perianth to polystemonous; filantherous (the filaments short). Anthers basifixed; non-versatile; dehiscing via longitudinal slits; latrorse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colpate.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 1–2 celled. Gynoecium syncarpous; synovarious (the styles free except at the very base); superior. Ovary 2 locular (basally and above), or 1 locular (in the mid-region, where the septum is lost); sessile. Gynoecium stylate. Styles 2; more or less free; from a depression at the top of the ovary; apical; much longer than the ovary. Stigmas 2. Placentation basal to axile. Ovules differentiated; 2 per locule; funicled; ascending; non-arillate; campylotropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle.

Fruit non-fleshy; indehiscent; capsular-indehiscent (somewhat inflated); 1 seeded. Seeds non-endospermic. Cotyledons 2. Embryo straight.

Physiology, phytochemistry. Anatomy non-C4 type. Mustard-oils absent (no myrosin cells).

Geography, cytology. Paleotropical. Tropical. Madagascar.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae (?); near Caryophyllales (?). Cronquist’s Subclass Hamamelidae; Urticales. APG 3 core angiosperms; core eudicot; Superorder Caryophyllanae; Order Caryophyllales.

Species 2. Genera 1; only genus, Physena.

General remarks. For a thorough descriptive account of Physena, see Dickison and Miller (1993) who provided ample evidence in support of a monogeneric family. However, its taxonomic affinities remain uncertain. (Gadek et al (1996) suggested that it might belong near Caryophyllales.

Illustrations. • Physena madagascariensis and P. sessilifora: Humbert, Fl. Madagascar (1946). • Physena madagascariensis: Nat. Pflanzenfam. III (1887).

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: 24th October 2017.’.