The Bladderwort's are the largest genus of carnivorous plants with approximately 230 species. They have a worldwide distribution, being found in most countries including several species here in England.
Generally, they are divided in to three groups-aquatic, terrestrial, and epiphytic, although there are exceptions to this. Aquatic species are normally free floating plants, found in open water in peat bogs-indeed this is the habitat that our own species are to be found. Terrestrial species live in permanently or seasonally waterlogged soils, and the epiphytes live on other plants-usually mosses on rocks or trees.
All species share the same characteristic small, bubble-like traps which are found all over the aquatic plants, and in the subterranean portions of the other two groups. They can't be called roots as the Bladderwort's have no true roots or leaves. Instead, they consist of modified stolons and rhizoids.
The traps themselves are the most highly developed structure of perhaps any plant, and are the fastest of all carnivorous plants. They are small (usually around 1-3mm in diameter), pressurised chambers complete with a trap door at one end.
When the trap is set and ready for capture, it's wall's are pulled in, giving them a concave appearence when seen from the outside and the bladder is sealed by the door. Any small swimming insect that blunders past the trap is guided towards the door by a series of bristles which bring the creature in to contact with tiny trigger hairs.
Once these are touched the door opens inwards and the insect and a quantity of water is sucked inside as the walls return to their convex states. The door then closes, and the water inside the trap is gradually pumped out leaving only the insect within. This whole scenario can take as little as a thousandth of a second. The trap is now re-set.
Digestive enzymes released in to the trap break down the insect, and the resulting nutrients are absorbed.