The families of flowering plants

L. Watson and M.J. Dallwitz

Myrothamnaceae Niedenzu

Habit and leaf form. Small xeromorphic shrubs (with rigid, opposite branches); resinous (from cells in the leaf epidermis). Xerophytic. Leaves small; opposite; flat, or folded (blackening and folding fanlike when dry, expanding and greening again after rain); more or less connate (the petiole bases of the opposite leaves sheathing); aromatic; simple. Lamina entire; oblong, or obovate (cuneate-flabellate or narrowly elliptic, toothed across the broadly rounded apex); palmately veined; without cross-venules. Leaves stipulate. Stipules intrapetiolar (subulate, on the sheathing petiole bases); free of one another; persistent (with the petioles). Lamina margins apically dentate. Vernation plicate.

Leaf anatomy. The leaf lamina bifacial. Stomata present; anomocytic. Hairs absent. The mesophyll containing crystals. The crystals druses.

Axial (stem, wood) anatomy. 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).

The wood diffuse porous. The vessels very small; solitary, or solitary and clustered (mostly solitary, with a few groups). The vessel end-walls very oblique; scalariform, or reticulately perforated and scalariform. The vessels without vestured pits. The axial xylem with tracheids; without vasicentric tracheids; with fibre tracheids; with libriform fibres, or without libriform fibres. The parenchyma apotracheal (or absent); wood not storied.

Reproductive type, pollination. Plants dioecious. Gynoecium of male flowers absent. Floral nectaries absent. Pollination anemophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in spikes, or in catkins. Inflorescences erect spikes or catkins. Flowers bracteate; regular; cyclic. Hypogynous disk absent.

Perianth absent.

Androecium 4, or 3–8. Androecial members free of one another (and 4), or coherent (when 3–8, then connate by their filaments). Androecium of male flowers, exclusively of fertile stamens. Stamens 3–8 (with large anthers). Anthers basifixed; non-versatile; dehiscing via longitudinal slits (? — not by valves); latrorse; more or less appendaged. The anther appendages apical (representing a small apical prolongation of the connective). Endothecium developing fibrous thickenings. Pollen shed in aggregates; in tetrads. Pollen grains aperturate; 3 aperturate; weakly colpate; 2-celled.

Gynoecium 3–4 carpelled. The pistil 3–4 celled. Gynoecium syncarpous; synovarious; superior. Ovary 3–4 locular. Gynoecium stylate. Styles 3–4; free; short, broad, recurved. Stigmas 3–4 (ventral, decurrent). Placentation axile. Ovules 10–50 per locule (‘rather numerous’); funicled; horizontal; biseriate; anatropous; bitegmic; crassinucellate. Endosperm formation nuclear.

Fruit non-fleshy; a schizocarp. Mericarps 3–4; comprising follicles (the carpels separating septicidally and opening ventrally). Seeds copiously endospermic. Endosperm oily. Seeds minute, or small. Embryo well differentiated. Cotyledons 2.

Physiology, phytochemistry. Not cyanogenic. Iridoids not detected. Proanthocyanidins present; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid present.

Geography, cytology. Paleotropical. Tropical. Southern tropical Africa, Madagascar. 2n = 20.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Hamamelidales. Cronquist’s Subclass Hamamelidae; Hamamelidales. APG III core angiosperms; core eudicot (informal group above Superorder not specified); Superorder Myrothamnanae. APG IV Order Gunnerales.

Species 2. Genera 1; only genus, Myrothamnus.

Illustrations. • Myrothamnus flabellifolia and M. moschatus: Nat. Pflanzenfam. iv (1895). • Myrothamnus flabellifolia (Hutchinson).

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: 5th March 2018.’.