in the motor cells if the hairs are stimulated several times. How this trigger
works is still little known. This shuts the two halves of the leaf sufficiently to
trap the insect and the leaf completes its shutting more slowly through normal
growth processes, crushing any animal that is caught. The waterwheel plant has
a similar but much smaller aquatic trap no more than 2 mm in diameter in
which it catches tiny aquatic animals.
The bladderworts have elaborate tiny bladders under water, 0.25–5 mm in
diameter. These are spherical to conical or cylindrical and water is extracted
from them until the walls are pulled inwards to develop considerable suction
pressure. There is a trap door that is kept closed but under tension. This is
released by an animal that triggers surrounding hairs and the animal is sucked
rapidly in by the pressure, after which the door immediately closes again, all
this taking about one hundredth of a second. The suction pressure is restored
after an hour or two.M7 – Carnivorous plants 225
(a) (b)Fig. 2. Leaf of the Venus fly-trap, Dionaea muscipula:(a) open; (b) shut.