Family Penaeaceae

Penaeaceae Guillemin

Excluding Oliniaceae, Rhynchocalycaceae

Habit and leaf form. Shrubs (typically small, often ericoid). Plants non-succulent. Leaves opposite (decussate); leathery; imbricate (often), or not imbricate; petiolate to sessile; simple. Lamina entire; pinnately veined (with a continuous marginal vein). Leaves stipulate (the stipules vestigial), or exstipulate.

Leaf anatomy. Stomata present; mainly confined to one surface, or on both surfaces; anomocytic.

Lamina dorsiventral, or isobilateral, or centric. The mesophyll with sclerencymatous idioblasts; containing calcium oxalate crystals. The mesophyll crystals druses.

Stem anatomy. Cork cambium present; initially deep-seated (in the pericycle). Nodes unilacunar. Cortical bundles present, or absent. Internal phloem present. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with tracheids; with vessels. Vessel end-walls simple. Primary medullary rays narrow.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers solitary to aggregated in ‘inflorescences’ (occasionally paired, often crowded); axillary (with the upper leaves); bracteate (the bracts often coloured); bracteolate (the bracteoles opposite, in one or more pairs); regular; 4 merous; cyclic; tricyclic. Free hypanthium present. Hypogynous disk absent.

Perianth sepaline (but the hypanthium and calyx often coloured like a corolla); 4; 1 whorled; sepaloid, or petaloid. Calyx 4; 1 whorled; polysepalous (as lobes on the hypanthium); regular; persistent (with the hypanthium); valvate.

Androecium 4. Androecial members free of the perianth (attached to the hypanthium); free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 4; isomerous with the perianth; alternisepalous; filantherous (the filaments very short). Anthers basifixed (the connective much expanded, thickly laminar, often much longer than the ventral or marginal, frequently well separated thecae); dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged, or unappendaged (?). Pollen shed as single grains. Pollen grains aperturate; 3–5 aperturate, or 6–10 aperturate; colpate and colporate (the colpi alternating with colpoid grooves).

Gynoecium 4 carpelled. Carpels isomerous with the perianth. The pistil 4 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary plurilocular; 4 locular; sessile. Gynoecium stylate. Styles 1; apical. Stigmas 1; capitate or four-lobed. Placentation basal to axile, or axile, or axile to apical. Ovules 2–4 per locule; pendulous, or ascending, or pendulous and ascending; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Penaea-type. Polar nuclei fusing prior to fertilization. Endosperm formation nuclear. Embryogeny asterad.

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal (surrounded by the persistent hypanthium). Seeds more or less non-endospermic. Embryo well differentiated. Cotyledons 2 (very small).

Seedling. Germination phanerocotylar.

Physiology, biochemistry. Aluminium accumulation not found.

Geography, cytology. Cape. Sub-tropical. Southernmost Africa. X = 11, 12.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Myrtiflorae; Myrtales. Cronquist’s Subclass Rosidae; Myrtales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Myrtales.

Species 25. Genera 7; Brachysiphon, Endonema, Glischrocolla, Penaea, Saltera, Sonderothamnus, Stylapterus.

Illustrations.
• Technical details: Penaea, ‘Sarcocolla’ (Lindley).
• Technical details: Saltera (Thonner).