Family Geissolomataceae

Geissolomataceae Endl.

Habit and leaf form. Small shrubs. Plants non-succulent. Xerophytic. Leaves evergreen; opposite; leathery; subsessile to sessile; simple. Lamina entire; pinnately veined. Leaves stipulate. Stipules intrapetiolar (on the petiole); free of one another; minute, vestigial. Lamina margins entire.

Leaf anatomy. Mucilaginous epidermis present. Stomata present; anomocytic.

Lamina dorsiventral. The mesophyll without sclerenchymatous idioblasts (by contrast with Penaeaceae); containing calcium oxalate crystals. The mesophyll crystals druses.

Stem anatomy. Young stems somewhat tetragonal. Cork cambium present; initially superficial. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Vessel end-walls oblique; scalariform.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers solitary; terminal (on short, axillary branches), or axillary; six bracteate (the bracts in three pairs, persistent); regular; 4 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent.

Perianth sepaline; 4; 1 whorled; petaloid; red to pink (rose). Calyx 4; 1 whorled; shortly gamosepalous; four blunt-lobed (nearly to the base). Calyx lobes markedly longer than the tube. Calyx persistent; imbricate.

Androecium 8. Androecial members free of the perianth to adnate (inserted at the base of the calyx); markedly unequal (the oppositisepalous members longer); free of one another; 2 whorled (4+4). Androecium exclusively of fertile stamens. Stamens 8; diplostemonous; alternisepalous (i.e. the outer cycle alternating with the sepals); filantherous (with slender filaments). Anthers dorsifixed (ellipsoid); versatile; dehiscing via longitudinal slits; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate.

Gynoecium 4 carpelled. Carpels isomerous with the perianth. The pistil 4 celled. Gynoecium syncarpous; synovarious to synstylovarious (the styles free below, but coherent above); superior. Ovary 4 locular (with four grooves and ridges, four lobed); sessile. Gynoecium stylate. Styles 4; partially joined (being coherent above); apical. Stigmas 4. Placentation axile to apical. Ovules 2 per locule; pendulous; collateral; non-arillate; anatropous; bitegmic. Outer integument contributing to the micropyle. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral.

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Fruit 4 seeded. Seeds endospermic. Embryo well differentiated (elongate). Cotyledons 2; linear, fleshy. Embryo central, straight. Testa shining.

Physiology, biochemistry. Aluminium accumulation demonstrated.

Geography, cytology. Cape. Sub-tropical to tropical. Southern Africa.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Hamamelidales. Cronquist’s Subclass Rosidae; Celastrales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Crossosomatales.

Species 1. Genera 1; only genus, Geissoloma.

Illustrations.
• Technical details: Geissoloma (Lindley).