The families of flowering plants.
Habit and leaf form. Shrubs, or lianas. Plants succulent. Self supporting, or climbing. Xerophytic. Leaves alternate; fleshy; petiolate; non-sheathing; simple. Lamina entire; ovate (or elliptic), or obovate; pinnately veined. Leaves exstipulate. Lamina margins entire (membranous).
Stem anatomy. Internal phloem absent. Secondary thickening anomalous; via concentric cambia. ‘Included’ phloem present. Xylem with tracheids. Sieve-tube plastids P-type; type III (b: with a polyhedral protein crystalloid, as well as the subperiferal proteinaceous filaments).
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in panicles (racemiform). The ultimate inflorescence unit cymose. Inflorescences terminal, or axillary; terminal racemiform thyrses or axillary cymes. Flowers bracteate; bi- bracteolate (the pedicels thickened upwards); regular; 5 merous; cyclic. Free hypanthium absent.
Perianthwith distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous; regular; persistent; imbricate. Corolla 5 (shorter than the sepals); 1 whorled; polypetalous; imbricate; regular. Petals slightly clawed (suborbicular).
Androecium 10. Androecial members free of the perianth (the oppositisepalous members), or adnate (the alternisepalous members being basaly joined to the petals); coherent; 1 adelphous (the filaments connate at the base); 1 whorled. Androecium exclusively of fertile stamens. Stamens 10; diplostemonous; both alternating with and opposite the corolla members; filantherous (the filaments subulate). Anthers dorsifixed; dehiscing via longitudinal slits; introrse. Pollen grains aperturate; 3 aperturate; colpate.
Gynoecium 3–5 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 1 celled. Gynoecium syncarpous; synstylovarious. Ovary 1 locular (the partitions ephemeral). Stigmas 3–5 (short, recurved). Placentation basal and free central (the ovules basal around a central column). Ovules in the single cavity 3–5 (as many as the stigmas); ascending; arillate; amphitropous.
Fruit non-fleshy; dehiscent; a capsule (leathery). Capsules 3–5 valvular (the valves opposite the sepals). Fruit 1–5 seeded (the seeds almost covered by the large, fleshy arils). Seeds non-endospermic. Perisperm present (mealy). Seeds with starch. Embryo well differentiated. Embryo curved.
Physiology, biochemistry. Ellagic acid present.
Geography, cytology. Neotropical. Sub-tropical to tropical. Mexico, Central America, West Indies.
Taxonomy.Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae; Caryophyllales. Cronquist’s Subclass Caryophyllidae; Caryophyllales. APG 3 core angiosperms; core eudicot; Superorder Caryophyllanae; Order Caryophyllales.
Species 3. Genera 1; only genus, Stegnosperma.