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Erect herbs, viscid, by longitudinal rows of minute, sessile glands and capitate-glandular hairs. Leaves linear to filiform, involute-coiled in vernation, exstipulate, spirally arranged. Flowers axillary, solitary, without bracteoles, 5-merous. Sepals imbricate, persistent, short-connate at the base. Petals larger than sepals, contorted, with a broad, dentate apex and cuneate base, oblique, ± connate at the very base. Stamens 5, sometimes unequal; Ovary superior, 2-celled, with ∞ ovules attached to the axis of the dissepiment about the middle; Capsule ± compressed, 2-celled, loculicid with 2 valves, sometimes the valves later splitting, the dissepiment splitting ± halfway. Seeds dark, rugose;


Asia-Tropical: NW. to NE. Australia: present SW. Australia: present South New Guinea: present
Two spp., one in SW. Australia, the other from NW. to NE. Australia, in Malesia: the N. Australian species in South New Guinea.


This is the fifth genus of insectivorous plants in Malesia, the others being Nepenthes, Utricularia, Drosera and Aldrovanda. Both species grow in depressions which are swampy on poor soils or which become swampy or water-logged in the wet season. Often gregarious.
The way of catching insects (small flies, mosquitoes, moths and ants) superficially resembles that in Drosera, but differs in that the capitate-glandular hairs make no movement towards the prey. RICA ERICKSON () calls it a 'flypaper trap of the passive type'. According to GRIEVE () "insects are usually first caught by the sticky mucilage exuded from the gland-tipped hairs and these tend to collapse or bend as they pour out secretion. The insect is thus also brought into contact with the numerous, minute sessile glands and becomes enveloped in additional secreted fluid. The process of secretion and absorption continues until all of the soft parts of the insect are dissolved and absorbed, and only the hard, indigestible parts remain. The glands then stop secretion and the stalked ones commence to recover to their normal position. In due course the hard parts of the insect which are left dry out and fall off."
It has been suggested that the capitate-glandular hairs secrete a sticky mucilage, but that the secretion of the sessile ones is less sticky and would serve mainly for digesting proteins, but I have no pertinent data to sustain this opinion.
The large West Australian species, B. gigantea, is well-known as the 'rainbow plant', a name "believed to be derived from the fact that on looking through the plant towards the setting sun, one can see a spectrum of colours where the edges of the leaves are bordered by the shining drops of liquid on the glands."


FENNER () gave a detailed account of the anatomy of the glands of B. gigantea LINDL.


VESTER - in Bot. Arch. 1940: map 192
DOMIN - in Act. Bot. Bohem. 1922: 1
SALISB. - in Bibl. Bot. 1929: 702
LANG - in Flora. 1901: 179
DIELS - in E. & P., Nat. Pfl. Fam., ed. 2, 18a. 1930: 288
BTH. - in Fl. Austr. 1864: 469