Cressa L.

Scientific Description

Family Convolvulaceae.

Habit and leaf form. Shrubs (subshrubs); laticiferous, or non-laticiferous and without coloured juice. Autotrophic. Plants with neither basal nor terminal concentrations of leaves. Helophytic, mesophytic, and xerophytic. Leaves minute to small; alternate; spiral; very shortly petiolate to sessile; non-sheathing; simple. Leaf blades entire; pinnately veined, or palmately veined; cross-venulate; obtuse at base. Leaves without stipules; without a persistent basal meristem. Leaf anatomy. Hairs present (hairs bifid). Stem anatomy. Nodes unilacunar. Secondary thickening anomalous, or developing from a conventional cambial ring; via concentric cambia, or from a single cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, forming a condensed leafy spike appearing as a terminal cluster. The terminal inflorescence unit cymose. Inflorescences terminal; with involucral bracts, or without involucral bracts. Flowers pedicellate to sessile; bracteate; bracteolate; small; regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present; annular. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; polysepalous; hairy; imbricate; persistent (enclosing fruit); with the median member posterior. Corolla 5; 1 -whorled; gamopetalous. Corolla lobes about the same length as the tube. Corolla imbricate and contorted; campanulate; regular; sparsely hairy abaxially (on mid-petaline bands); white, or pink. Androecium 5. Androecial members adnate (to the corolla); all equal to markedly unequal (actually subequal); free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5. Staminal insertion near the base of the corolla tube. Stamens becoming exserted; oppositisepalous. Filaments glabrous (or tuberculate towards the base). Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Pollen grains psilate. Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; synovarious to synstylovarious (depending on interpretation of partially joined styles); superior. Ovary plurilocular; 2 locular. Gynoecium median. Ovary summit hairy, the hairs not confined to radiating bands (hairy in upper half). Styles 2; free, or partially joined (rarely, connate at the base); simple (filiform); apical. Stigmas 2; 1 - lobed; capitate (large); dry type; papillate; Group II type. Placentation basal. Ovules 2 per locule; ascending; apotropous; non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; hairy (villous in upper half); dehiscent; a capsule. Capsules loculicidal (via 2–4 valves). Fruit 2 locular; 1 seeded, or 2 seeded. Seeds irregular in outline; endospermic. Endosperm oily. Seeds small; not conspicuously hairy. Cotyledons 2. Embryo chlorophyllous; straight, or curved. Seedling. Germination phanerocotylar.

Physiology, biochemistry. Aluminium accumulation not found. Photosynthetic pathway: C₃.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, Queensland, New South Wales, Victoria, and Australian Capital Territory. Northern Botanical Province and Eremaean Botanical Province.

Additional characters Stigmas the stigmatic area globose. Corolla lobes spreading.