Habit and leaf form. Small shrubs. ‘Normal’ plants. To 0.2–0.5 m high. Mesophytic. Leaves small; not fasciculate; whorled; 8–11 per whorl; not decurrent on the stems; not imbricate; sessile; simple; epulvinate. Leaf blades entire; flat, or rolled; linear; one-veined, or pinnately veined. Mature leaf blades adaxially glabrous, or pubescent. Leaves without stipules. Leaf blade margins entire; revolute. Leaf anatomy. Hairs present, or absent. Branched hairs absent. Stem anatomy. Nodes unilacunar. Secondary thickening developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous.
Inflorescence and flower features. Flowers solitary (axillary, pedunculate); axillary; 1 per axil; pedicellate; one or more bracteate. Bracts persistent. Flowers small; regular; 5 merous; tetracyclic (if the stamens are interpreted as one whorl). Floral receptacle with neither androphore nor gynophore; not markedly hollowed. Flowers not enclosed in the succulent receptacle. Free hypanthium absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; polysepalous; valvate (secured by hairs in the bud); exceeded by the corolla; neither appendaged nor spurred; green and red; non-fleshy; not persistent; non-accrescent; with the median member posterior. Sepals narrowly ovate. Corolla present; 5; 1 -whorled; polypetalous; induplicate valvate; regular; glabrous abaxially; glabrous adaxially; with contrasting markings; purple and red; deciduous; non-accrescent. Petals obovate; sessile; not hooded; not navicular. Corolla members entire (apiculate). Androecium present. Androecial members definite in number. Androecium 10. Androecial members ambiguously branched (sometimes basally joined), or unbranched. Androecial sequence not determinable. Androecial members free of the perianth; markedly unequal (outer whorl shorter than inner whorl); free of one another; 2 -whorled. Stamens 10; becoming exserted; not didynamous, not tetradynamous; all more or less similar in shape; diplostemonous; alternisepalous (in antepetalous pairs); all opposite the corolla members; erect in bud; filantherous (with very short filaments or virtually sessile). Filaments glabrous; strap-shaped. Anthers cohering (by means of hairs); dimorphic (with different length apical tubes); basifixed; incurved; non-versatile (broad at their junction with the filament); dehiscing via pores (each anther by a single apical pore, this terminating a long tube); four locular (the locules in a linear series); tetrasporangiate; appendaged. The anther appendages apical (consisting of a long tube ending in a pore). Gynoecium 2 carpelled. The pistil 2 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous; eu-syncarpous; superior. Ovary plurilocular; 2 locular. Gynoecium median. Ovary sessile. Ovary summit hairy, the hairs not confined to radiating bands. Gynoecium stylate. Styles 1; simple; attenuate from the ovary; apical; much longer than the ovary at anthesis; not becoming exserted; deciduous; hairy (in the lower part). Style hairs not brush-like. Stylar canal present. Stigmas 1; 1 - lobed; clavate. Placentation axile, or apical. Ovulodes absent. Ovules 1 per locule; pendulous; apotropous; with ventral raphe; non-arillate; anatropous.
Fruit and seed features. Fruit 5–7 mm long; sessile; falling from the plant before the next growing season; non-fleshy; hairy; dehiscent; a capsule. Capsules loculicidal. Fruit 2 celled. Dispersal unit the seed. Fruit 1–2 seeded. Seeds 1 per locule. Seeds endospermic; not mucous; not compressed (trigonous); small; non-arillate; conspicuously hairy (the hairs inflated or flat, deflated); without a tuft of hairs. Cotyledons 2. Testa hard; hairy (sometimes erroneously stated to be glabrous); homogeneous in colour.
Geography, cytology, number of species. Australian. World distribution: Australia. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia. South-West Botanical Province. A genus of 2 species; 2 species in Western Australia; 2 endemic to Western Australia.
Additional comments. Differential characters in Tremandraceae: hair type, leaf arrangement, flower -merosity, corolla aestivation, stamen series number and equality, anther locule number and series number, filament form, filament/anther junction, anther tube presence and length, ovules per locule, ovule/seed appendage presence, seed hair type.
Etymology. From the Greek for "flat, wide, broad" and "box"; the anthers comprise four parallel cells in a single plane.