The families of flowering plants

L. Watson and M. J. Dallwitz

Frankeniaceae S.F. Gray

Habit and leaf form. Sub- shrubs, or herbs (with jointed stems). Perennial. Xerophytic (and halophytic). Leaves evergreen; small; opposite (decussate, often ericoid); rolled; petiolate; simple; epulvinate. Lamina entire; linear. Leaves dubiously stipulate (some Frankenia species), or exstipulate (mostly). Lamina margins revolute. Leaf development not ‘graminaceous’.

Leaf anatomy. The leaf lamina sub- centric (in some species), or dorsiventral (generally, more or less, in species with revolute leaf margins); exhibiting epidermal salt glands (these located in pits or grooves, each consisting of about six cells derived from division of a single cell, with the uppermost two resembling a pair of guard-cells in surface view: see illustration). Stomata present; mainly confined to one surface (abaxial, usually sunken); anomocytic. Hairs present; (as distinct from the salt glands) eglandular; unicellular. Unicellular hairs simple (but sometimes tufted). Complex hairs absent. Adaxial hypodermis absent. Lamina without secretory cavities. The mesophyll with sclerenchymatous idioblasts (around the veins), or without sclerenchymatous idioblasts. Minor leaf veins with phloem transfer cells (Frankenia).

Axial (stem, wood) anatomy. Young stems eventually with hollow internodes. Pith homogeneous. Secretory cavities absent. Cork cambium present; initially superficial (usually), or initially deep-seated (in Anthobryum). Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Secondary thickening in some species presumably developing from a conventional cambial ring (?), or anomalous. The anomalous secondary thickening when present, in Frankenia, via concentric cambia. Primary medullary rays lacking.

The wood diffuse porous (“scattered”). The vessels small; solitary (?). The vessel end-walls simple. The vessels without spiral thickening. The axial xylem with libriform fibres. ‘Included’ phloem present, or absent. The wood partially storied (VPI).

Reproductive type, pollination. Plants hermaphrodite (usually), or polygamomonoecious (occasionally unisexual — Niederlinia). Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes. The ultimate inflorescence units cymose. Inflorescences axillary; dichasial. Flowers bracteate; (bi-) bracteolate; regular; cyclic; tetracyclic, or pentacyclic.

Perianth with distinct calyx and corolla; 8–14; 2 whorled; isomerous. Calyx 4–7; 1 whorled; gamosepalous; shortly blunt-lobed. Calyx lobes markedly shorter than the tube. Calyx regular; persistent; induplicate valvate. Corolla 4–7; 1 whorled; appendiculate (each petal with a scale at the base of the limb, continued down the sides of the claw); polypetalous; imbricate; regular; persistent. Petals clawed; bilobed, or fringed.

Androecium (4–)6(–24). Androecial members free of the perianth; all equal, or markedly unequal; more or less coherent; 1 adelphous (basally connate); 2 whorled (usually 3+3). Androecium exclusively of fertile stamens. Stamens (4–)6(–24); isomerous with the perianth, or diplostemonous to polystemonous. Anthers versatile; dehiscing via longitudinal slits; extrorse. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Tapetum glandular. Pollen grains aperturate; (2–)3(–4) aperturate, or 6 aperturate; colpate, or rugate; 3-celled.

Gynoecium (2–)3(–4) carpelled. The pistil 1 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary 1 locular. The ‘odd’ carpel posterior. Styles 1; apical. Stigmas (2–)3(–4); dry type; papillate; Group II type. Placentation parietal (with (2-)3(-4) placentae). Ovules in the single cavity 12–100 (i.e. ‘many’); ascending; non-arillate; anatropous; bitegmic; pseudocrassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; large. Synergids hooked.

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal and valvular (enclosed by the calyx). Seeds copiously endospermic. Endosperm not oily (starchy). Seeds with starch. Cotyledons 2. Embryo straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. C3. C3 physiology recorded directly in Frankenia, Hypericopsis. Anatomy non-C4 type (Frankenia, Hypericopsis). Not cyanogenic. Alkaloids absent (2 species). Saponins/sapogenins absent. Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present; quercetin, or kaempferol and quercetin. Ellagic acid present, or absent (variable in Frankenia). Aluminium accumulation not found. Sieve-tube plastids S-type.

Geography, cytology. Mostly temperate and sub-tropical (halophytes). Widespread arid and maritime. X = 10, 15.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Violiflorae; Tamaricales. Cronquist’s Subclass Dilleniidae; Violales. APG 3 core angiosperms; core eudicot; Superorder Caryophyllanae; Order Caryophyllales.

Species 90. Genera 4; Frankenia, Hypericopsis, Anthobryum, Niederleinia.

Illustrations. • Technical details: Frankenia. • Frankenia laevis: Eng. Bot. 190, 1864. • Frankenia laevis (B. Ent., 1835). • Foliar epidermis of Frankenia pulverulenta, with glands: Solereder, 1908.

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: 19th October 2016.’.