Family Dicksoniaceae

Dicrastylidaceae J. Drumm. ex Harv.

Alternatively Chloanthaceae Hutch.~ Verbenaceae or Labiatae

Habit and leaf form. Shrubs (often tomentose). ‘Normal’ plants to switch-plants (Spartothamnella), or ‘normal’ plants. Leaves well developed (though sparse and contributing to the broomlike habit of Spartothamnella). Mesophytic, or xerophytic. Leaves evergreen; opposite, or whorled (rarely alternate); ‘herbaceous’, or leathery; subsessile to sessile; aromatic (?), or without marked odour (Physopsideae); simple. Lamina entire; linear, or lanceolate, or oblong, or ovate; pinnately veined; cross-venulate. Leaves exstipulate; without a persistent basal meristem.

Leaf anatomy. Hairs present. Complex hairs present; peltate, or stellate.

Stem anatomy. Internal phloem absent. Secondary thickening anomalous; via concentric cambia (all the genera). ‘Included’ phloem present. Xylem with fibre tracheids.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes, in panicles, in heads, in corymbs, and in spikes. Inflorescences terminal, or axillary; spicate, capitate or compound. Flowers bracteate; regular, or somewhat irregular, or very irregular; when irregular, zygomorphic. The floral irregularity (when manifest) involving the perianth, or involving the perianth and involving the androecium. Flowers neither papilionaceous nor pseudo-papilionaceous; 4–8 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent.

Perianth with distinct calyx and corolla; 8–16; 2 whorled; isomerous. Calyx 4–8; 1 whorled; gamosepalous; regular; persistent; accrescent (rarely, enlarging in the fruit), or non-accrescent. Corolla 4–8 (or almost truncate); 1 whorled; gamopetalous; imbricate; more or less unequal but not bilabiate to bilabiate (usually), or regular.

Androecium 4–8, or 3–7. Androecial members adnate (epipetalous); free of one another; 1 whorled. Androecium exclusively of fertile stamens (mostly), or including staminodes (Hemiphora). Staminodes in Hemiphora 2; in the same series as the fertile stamens; representing in Hemiphora, the posterior-lateral pair. Fertile stamens representing the posterior median member, the posterior-lateral pair, and the anterior-lateral pair, or the posterior-lateral pair and the anterior-lateral pair, or the anterior-lateral pair. Stamens 4–8, or 3–7, or 2 (Hemiphora); inserted near the base of the corolla tube, or midway down the corolla tube, or in the throat of the corolla tube; reduced in number relative to the adjacent perianth, or isomerous with the perianth (usually as many as the corolla lobes or one fewer); oppositisepalous; alternating with the corolla members. Anthers dorsifixed; dehiscing via longitudinal slits (mostly), or dehiscing by longitudinal valves (Hemiphora); appendaged (in Pityrodia), or unappendaged. The anther appendages of Pityrodia basal. Pollen grains aperturate; 3 aperturate; colpate.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2 celled, or 4 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 2 locular (morphologically), or 4 locular (sometimes, ostensibly, by intrusion from the walls of ‘false septa’). Locules secondarily divided by ‘false septa’, or without ‘false septa’. Gynoecium median. Styles 1; apical. Stigmas 1 (e.g. Newcastelia, Physopsis), or 2 (mostly). Placentation axile. Ovules 2 per locule, or 1 per locule (when ‘false cells’ are interpreted as locules); non-arillate; hemianatropous; unitegmic; tenuinucellate. Polar nuclei fusing only after one has been fertilized, or fusing simultaneously with the male gamete (?). Antipodal cells formed; not proliferating; ephemeral. Synergids hooked.

Fruit non-fleshy (usually), or fleshy (rarely); indehiscent; a drupe, or a nut. The drupes with separable pyrenes (these two, representing the ‘true’ locules), or with one stone. Fruit 1–2 seeded. Seeds endospermic (mostly), or non-endospermic (Spartothamnella). Embryo straight.

Physiology, biochemistry. Not cyanogenic. Iridoids detected. Proanthocyanidins absent.

Geography, cytology. Temperate to tropical. Tropical East Africa, Madagascar, Mascarenes, Australasia, Pacific.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Lamiiflorae; Lamiales. Cronquist’s Subclass Asteridae; Lamiales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; lamiid; Order Lamiales (as a synonym of Labiatae).

Species 90. Genera 11; Chloanthes, Cyanostegia, Denisonia, Dicrastylis, Hemiphora, Lachnostachys, Mallophora, Newcastelia, Physopsis, Pityrodia, Spartothamnella.

These genera are part of the Labiatae/Verbenaceae problem: see remarks under Labiatae.