The families of flowering plants.
AlternativelyTremandreae (Tremandraceae) R. Br.~ Elaeocarpaceae
IncludingTetrathecaceae R. Br.
Habit and leaf form. Small shrubs, or herbs (slender subshrubs, or subherbaceous). ‘Normal’ plants, or switch-plants; sometimes with the principal photosynthesizing function transferred to stems. Leaves well developed, or much reduced, or absent. Perennial. Mesophytic, or xerophytic. Leaves minute, or small; alternate, or opposite, or whorled; flat, or rolled (often ericoid); ‘herbaceous’, or leathery, or membranous; imbricate (often), or not imbricate; petiolate to sessile; non-sheathing; simple. Lamina entire; one-veined, or pinnately veined; cross-venulate, or without cross-venules. Leaves exstipulate (as usually interpreted, but often with glands at the stipular positions). Lamina margins entire, or dentate. Leaves without a persistent basal meristem.
Leaf anatomy. Mucilaginous epidermis present, or absent. Stomata present; mainly confined to one surface (abaxial); anomocytic.
Lamina dorsiventral. The mesophyll containing calcium oxalate crystals. The mesophyll crystals druses, or solitary-prismatic.
Stem anatomy. Nodes unilacunar. Secondary thickening developing from a conventional cambial ring. Xylem with libriform fibres; with vessels. Vessel end-walls simple, or scalariform and simple. Primary medullary rays narrow. Wood parenchyma scanty paratracheal (or absent).
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers solitary (slender-pedunculate), or aggregated in ‘inflorescences’; axillary. Inflorescences (when flowers grouped) axillary (with 2–4 flowers per axil). Flowers bracteate (at the peduncle base); small; regular; (3–)4 merous, or 5 merous; cyclic; tetracyclic (if the stamens are interpreted as one whorl). Free hypanthium absent. Hypogynous disk present, or absent.
Perianthwith distinct calyx and corolla; 6, or 8, or 10; 2 whorled; isomerous. Calyx (3–)4–5; 1 whorled; polysepalous (usually), or gamosepalous; regular; valvate; with the median member posterior. Corolla (3–)4–5; 1 whorled; polypetalous; induplicate valvate; regular; white, or pink, or purple.
Androecium 6 (rarely), or 8, or 10. Androecial members branched (this being a reasonable interpretation of the antepetalous pairs), or unbranched (as conventionally interpreted); free of the perianth; free of one another, or coherent; 4 adelphous, or 5 adelphous (interpreting the pairs as ‘bundles’); 1 whorled (seemingly, though twice the corolla in number). The androecial bundles if interpreted as ‘bundled’, opposite the corolla members. Androecium exclusively of fertile stamens. Stamens 6 (rarely), or 8, or 10; diplostemonous; alternisepalous (in antepetalous pairs); opposite the corolla members; erect in bud; filantherous (with short filaments). Anthers basifixed; non-versatile; dehiscing via pores (with a single apical pore, this often at the top of a more or less elongated tube); four locular; tetrasporangiate (the sporangia sometimes in a single row); appendaged (i.e. with an apical pore-tipped tube), or unappendaged. Pollen grains aperturate; 3 aperturate; colporate (or colporoidate); 2-celled.
Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 2 locular. Gynoecium median; stylate. Styles 1; apical. Placentation axile, or apical. Ovules 1–2(–5) per locule; pendulous; epitropous; with ventral raphe; arillate (usually), or non-arillate (Platytheca); anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Antipodal cells formed; 3; not proliferating.
Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal, or septicidal and loculicidal. Seeds endospermic; winged (via a twisted appendage), or wingless. Cotyledons 2 (?). Embryo straight.
Physiology, biochemistry. Cyanogenic, or not cyanogenic. Alkaloids present, or absent (2 species listed). Iridoids not detected. Proanthocyanidins absent. Flavonols present; quercetin and myricetin. Ellagic acid present (Tetratheca), or absent (Platytheca). Aluminium accumulation not found.
Geography, cytology. Temperate to tropical. Australia.
Taxonomy.Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Araliiflorae (?); Pittosporales (?). Cronquist’s Subclass Rosidae; Polygalales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Oxalidales (as a synonym of Elaeocarpaceae).
Species about 45. Genera 3; Platytheca, Tetratheca, Tremandra.
General remarks. This family exemplifies the well known difficulties in distributing certain Dicot families between Dahlgren’s Araliiflorae and Corniflorae. It is equally hard to assign them with confidence to the higher level groupings Crassinucelli and Tenuinucelli. This is interesting, given that the latter evidently represent a major divergence in the Dicot line of descent (cf.Young and Watson 1970, Chase et al. 1993).