Hydrolea L.

Scientific Description

Family Hydrophyllaceae.

Habit and leaf form. Sub- shrubs, or herbs. Plants spiny (sometimes), or unarmed. Perennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Helophytic to mesophytic. Leaves alternate; spiral; petiolate to subsessile; non-sheathing; without marked odour, or foetid; simple. Leaf blades entire; pinnately veined, or palmately veined; cross-venulate. Leaves without stipules; without a persistent basal meristem. Leaf anatomy. Glandular hairs present (often), or absent. Stem anatomy. Nodes unilacunar. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous; via hymenoptera.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes (forming panicles, or in false racemes or axillary clusters). The terminal inflorescence unit cymose. Inflorescences axillary, or leaf-opposed. Flowers regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; gamosepalous (basally); deeply lobed; hairy to glabrous; imbricate; regular. Epicalyx absent. Corolla 5; 1 -whorled; appendiculate, or not appendiculate; gamopetalous; deeply lobed; imbricate; rotate to campanulate; regular; blue. Androecium 5. Androecial members adnate (to the corolla tube); all equal; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5. Staminal insertion in the throat of the corolla tube. Stamens isomerous with the perianth; oppositisepalous (alternating with the petals); all alternating with the corolla members. Filaments filiform, usually dilated at the base. Anthers sagittate; dorsifixed; versatile; dehiscing via longitudinal slits; introrse; appendaged. Gynoecium 2(–3) carpelled. The pistil 2(–3) celled. Gynoecium syncarpous; synovarious; superior. Ovary plurilocular; 2(–3) locular. Gynoecium median; stylate. Styles 2 (spreading); free; attenuate from the ovary; apical. Stigmas capitate (or ‘simple’); dry type; papillate; Group II type. Placentation axile. Ovules 10–50 per locule (i.e. ‘numerous’); funicled, or sessile; pendulous (when funicled); epitropous; non-arillate; anatropous, or amphitropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal (via 2 valves), or splitting irregularly. Fruit 10–50 seeded (i.e. ‘numerous’). Seeds copiously endospermic. Endosperm oily. Cotyledons 2. Embryo straight. Seedling. Germination phanerocotylar.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, and Queensland. Northern Botanical Province.