• Choose a category
• All
• Classic-Fiction

By Root 507 0

observers not prepared for it; one instant the animalcule is swimming against the bladder, the next it is beating against the prison walls in vain search for an exit from its death cell. Once inside, the animal usually dies, but often not until it has been for several days a prisoner. It is slowly digested by an enzyme so weak that some researchers failed to demonstrate its presence, then its substance is absorbed by the quadrifid hairs, while benzoic acid in the trap fluid prevents the multiplication of bacteria. The same bladder may be sprung repeatedlyup to fourteen times in three daysand resets itself each time in half an hour or less, even while digesting its latest booty, until a number of living, dying, and partly digested victims are simultaneously present.

A hole punched in the wall by a needle, or a hair inserted between the valve and the sill, permitting water to enter, prevents resetting of the trap, which remains permanently distended. Cold, heat, and moderate concentrations of a poison may prevent the resetting of a sprung bladder by inhibiting absorption of water from the cavity by active cells, but unless they destroy the turgor of the wall cells, they do not prevent the springing of a set bladderall of which is evidence that this is a mechanical process effected by the release of tensions in the enclosing tissues. This conclusion

Page 128

is strengthened by the failure of electrical or chemical stimulation, which cause the sensitive leaves of Dionaea or Aldrovanda to close, to have a corresponding effect upon the bladders, which respond only to physical contact.

The bladderwort's prey includes almost any creature that swims in its native pond or ditch and is small enough to pass through the bladder's mouth. Various small crustaceansespecially copepods, ostracods, and cladoceranseel worms, rotifers or wheel animalcules, and infusoria are frequent victims. Mosquito larvae are so often caught that bladderworts have been considered as a means of combatting these pests. Tadpoles are sometimes swallowed headfirst; and newly hatched fishes that have the misfortune of becoming entangled among bladderworts may be seized by their heads, tails, or still-attached yolk sacs. Mosquito wrigglers and diminutive vertebrates too large to be sucked in all at once are held while the valve clamps down on them, sometimes firmly enough to prevent, or at least retard, the inflow of water while it is removed by the quadrifid hairs, with the result that these victims are drawn slowly inward until they are wholly immured and digested.

The number of small creatures held captive by a single plant at one time may be enormous. Part of a greater bladderwort with combined length of main stem and branches of seven feet (220 cm.) bore approximately 13,860 bladders. The number of small crustaceans in each of ten bladders ranged from six to twenty-two, with an average of twelve, whence it was estimated that this part of the plant contained about 150,000 of these animals, in addition to a multitude of organisms of other kinds. A century ago, M. Büisgen (1888) made a few experiments which showed that bladderworts in water with no lack of small animals grew twice as fast as those in water from the same source from which most had been strained.

The small minority of flowering plants that have become carnivorous belong to six families, with traps of diverse forms, which have apparently evolved independently no less than eight times. None has lost its chlorophyll and capacity to synthesize carbohydrates, which it supplements with amino acids derived from the digestion of small animals. These paradoxical plants combine animal and vegetable

Page 129

modes of nutrition. They appear to approach animals halfway, which prompts us to ask whether any animal takes a complementary course and develops chlorophyll to synthesize at least part of its carbohydrates, while it continues to eat plants or other animals. As far as I know, none does. The chloroplasts found in the bodies of a few animals belong to symbiotic algae,