Habit and leaf form. Small trees, or shrubs. Switch-plants; with the principal photosynthesizing function transferred to stems (and the green, striate branches ending in spines). Leaves much reduced (represented by minute, deltoid scales, above each of which is a conspicuous, black, triangular gland field). Xerophytic. Leaves minute; alternate; membranous.
Stem anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Wood parenchyma apotracheal.
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes. The ultimate inflorescence unit cymose. Inflorescences lateral; short, 3–7 flowered cymes. Flowers minutely bracteate; regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent.
Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5 (small, minutely glandular-fringed); 1 whorled; gamosepalous (connate basally); regular; persistent; imbricate. Corolla 5; 1 whorled; polypetalous; imbricate; regular; thickish, carinate within; deciduous.
Androecium 5. Androecial members free of the perianth; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members; filantherous (the filaments subulate, persistent). Anthers apically introrse.
Gynoecium 5 carpelled. Carpels isomerous with the perianth. The pistil 5 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 5 locular. Gynoecium stylate. Styles 1; apical (thick, persistent). Stigmas 1; 5 lobed. Placentation axile. Ovules (3–)6 per locule; horizontal; biseriate; amphitropous.
Fruit non-fleshy (woody); dehiscent; a capsule. Capsules septicidal and loculicidal (partially loculicidal from the top). Seeds endospermic (the endosperm thin, fleshy); ascending, 1–2 per loculus; winged (the wing basal, membranous). Embryo straight.
Geography, cytology. Holarctic. Temperate to sub-tropical. Southwest U.S.A.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Santaliflorae (?); Celastrales (?). Cronquist’s Subclass Rosidae; Celastrales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Celastrales (as a synonm of Celastraceae).
Species 2. Genera 2; Acanthothamnus, Canotia.