The families of flowering plants

L. Watson and M.J. Dallwitz

Penthoraceae Van Tiegh.

~ Saxifragaceae.

Habit and leaf form. Erect herbs. Perennial; rhizomatous. Helophytic. Leaves alternate; petiolate, or sessile; not gland-dotted; simple. Lamina entire; lanceolate; pinnately veined; attenuate to the base. Leaves exstipulate. Lamina margins serrate.

Axial (stem, wood) anatomy. Nodes unilacunar. Secondary thickening absent, or developing from a conventional cambial ring, or anomalous (?).

The axial xylem with fibre tracheids.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes. The ultimate inflorescence units cymose. Inflorescences terminal; terminal, secund cymes. Flowers small; regular; 5(–8) merous; cyclic; tetracyclic, or pentacyclic. Free hypanthium present.

Perianth with distinct calyx and corolla, or sepaline (usually without a corolla); 5(–8), or 10(–16); 1 whorled, or 2 whorled; when two-whorled, isomerous. Calyx 5(–8); 1 whorled; polysepalous (on the hypanthium); regular; persistent; valvate. Corolla when present, 5(–8) (inconspicuous); 1 whorled; polypetalous.

Androecium 10(–16) (?). Androecial members free of the perianth (inserted at the mouth of the hypanthium); free of one another; 2 whorled (usually 5+5). Androecium exclusively of fertile stamens. Stamens 10; filantherous (the filaments filiform). Anthers basifixed; dehiscing via longitudinal slits. Pollen grains aperturate; 3 aperturate; colporate (colporoidate).

Gynoecium (4–)5(–8) carpelled. Carpels isomerous with the perianth. The pistil (4–)5(–8) celled (below). Gynoecium apocarpous to syncarpous; semicarpous (the carpels united in the lower half); partly inferior (slightly sunk in the receptacle). Carpel stylate (recurved, with a short style and capitate stigma); 30–100 ovuled (‘many’). Placentation marginal (each carpel with a single, marginal, pendulous placenta in its distal, free part). Ovary 5(–8) locular (below).

Fruit non-fleshy; not an aggregate. The fruiting carpel dehiscent; a follicle (the 5(–8) follicles circumscissile above their union). Fruit many seeded. Seeds scobiform; not conspicuously hairy (papillose).

Physiology, phytochemistry. Not cyanogenic.

Geography, cytology. Holarctic and Paleotropical. Temperate to tropical. Eastern Asia, Indochina, Atlantic North America.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Saxifragales (?). Cronquist’s Subclass Rosidae; Rosales. APG III core angiosperms; core eudicot; unplaced at Superordinal level. APG IV Order Saxifragales.

Species 3. Genera 1; only genus, Penthorum.

Economic uses, etc. Edible after cooking, but may be laxative.

Illustrations. • Penthorum sedoides: de Candolle, Memoires 2 (1828). • Penthorum sedoides: Millspaugh, Am. Medicinal Plants 1 (1892). • Flower and dehiscing carpels of Penthorum sedoides: Nat. Pflanzenfam. III (1891).

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: 15th April 2018.’.