Habit and leaf form. Small trees, or shrubs (with long- and short-shoots, the petioles of the leaves on the long-shoots hardening and persisting as spines when the blades fall, the short-shoots axillary to the spines and producing clustered leaves that do not form spines). Switch-plants; more or less ‘cactoid’, or with the principal photosynthesizing function transferred to stems. Plants succulent (often with parenchymatized xylem storing water). Xerophytic. Leaves deciduous (often ephemeral, produced after rain); small; alternate; fleshy; petiolate; non-sheathing; simple. Lamina entire; pinnately veined. Leaves exstipulate.
Leaf anatomy. Mucilaginous epidermis present. Stomata present; anomocytic.
Minor leaf veins without phloem transfer cells (Idria).
Stem anatomy. Cork cambium present; initially deep-seated, or superficial. Nodes unilacunar (with one trace). Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids; with vessels. Vessel end-walls simple. Wood parenchyma apotracheal. Pith with diaphragms.
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’. Inflorescences terminal, or axillary. Flowers showy, medium-sized; regular to somewhat irregular; sometimes slightly zygomorphic (curved); cyclic; tetracyclic, or pentacyclic. Free hypanthium absent. Hypogynous disk present; annular (small).
Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous; persistent; much imbricate. Corolla 5; gamopetalous; imbricate; tubular; unequal but not bilabiate, or regular; yellow (Idria), or red (Fouquieria).
Androecium 10–15(–23). Androecial members free of the perianth; all equal, or markedly unequal; free of one another; 1–2 whorled (the antesepalous members sometimes larger and more outwardly directed, simulating two whorls). Androecium exclusively of fertile stamens (?). Stamens 10–15(–23); diplostemonous, or triplostemonous; both alternating with and opposite the corolla members; long filantherous (exserted, the filaments often hairy at the base). Anthers dorsifixed; dehiscing via longitudinal slits; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate; 2-celled.
Gynoecium 3 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; synovarious to synstylovarious; superior. Ovary 1 locular. Gynoecium stylate. Styles 3; partially joined (the style branched near or above the middle); apical. Stigmas 3 (terminal). Placentation parietal (above, with deeply intruded placentas, axile at the base). Ovules in the single cavity (6–)14–18(–20); ascending; anatropous; bitegmic; tenuinucellate. Outer integument not contributing to the micropyle. Endothelium differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped. Endosperm formation cellular. Embryogeny asterad.
Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Seeds endospermic, or non-endospermic. Endosperm when present, oily. Seeds winged. Embryo well differentiated. Cotyledons 2. Embryo straight (spathulate).
Seedling. Germination phanerocotylar.
Physiology, biochemistry. Not cyanogenic. Alkaloids absent (6 species). Iridoids detected; ‘Route I’ type (normal). Proanthocyanidins present, or absent. Ellagic acid present. Saponins/sapogenins present. C3. C3 physiology recorded directly in Fouquieria.
Geography, cytology. Neotropical. Sub-tropical. Warm Southeast U.S.A. and Central America. X = 12.
Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Fouquieriales. Cronquist’s Subclass Dilleniidae; Violales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Ericales.
Species 11. Genera 2; only genera, Fouquieria, Idria.