Family Penthoraceae

Penthoraceae Van Tiegh.

~ Saxifragaceae

Habit and leaf form. Erect herbs. Perennial; rhizomatous. Helophytic. Leaves alternate; sessile; simple. Lamina entire; lanceolate; pinnately veined; attenuate at the base. Leaves exstipulate. Lamina margins serrate.

Stem anatomy. Nodes unilacunar. Secondary thickening absent, or developing from a conventional cambial ring, or anomalous (?). Xylem with fibre tracheids.

Reproductive type, pollination. Plants hermaphrodite.

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

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; regular; persistent; valvate. Corolla when present, 5(–8) (inconspicuous); 1 whorled; polypetalous.

Androecium 10(–16) (?). Androecial members free of the perianth; free of one another; 2 whorled (usually 5+5). Androecium exclusively of fertile stamens. Stamens 5(–8) (?); filantherous (the filaments filiform). Anthers basifixed (basifixed). Pollen grains aperturate; 3 aperturate; colporate (colporoidate).

Gynoecium 5(–8) carpelled. Carpels isomerous with the perianth. The pistil 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, biochemistry. 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 3 core angiosperms; core eudicot; unplaced at Superordinal level; Order Saxifragales.

Species 3. Genera 1; only genus, Penthorum.