Carnivorousnes is a state that implies for the plant not only the ability to capture animals but also to digest them.
The carnivorous plants comprise more than 500 species growing naturally; they are grouped into 7 families. They are all phanerogams ( plants with flowers).
There is a large morphological diversity in the carnivorous plants. Their size varies according to the species, from a fraction of an inch in the smallest to over 60 ft in the largest, which develop as climbing vines. Depending on the habit, polymorphism may also exist within the same species. This is the case with Nepenthes vieillardii ( Nepenthaceae family), a carnivorous plant found in New Caledonia from sea level, where the minimum temperature is about 16 degree C, to 3500 ft. (1100m), where the thermometer sometimes drops to freezing point.
The flowers are equally variable between genera. They often have a brief life, but stand about the surrounding vegetation on their stalks and prove most efficient at attracting insects. the flowers of carnivorous plants bear no capture mechanism, this function being the sole prerogative of the traps. their raison de'etre, as with the other flowering plants, is multiplication and thus the survival of the species. The traps could be in the form of an active steel trap, active mousetrap, active fly-paper trap and passive pitfall trap.
Why have some plant species, often biologically quite distinct from each other, developed this extraordinary property called carnivorousness. In order to grow and reproduce, plants require certain essential elements - oxygen, carbon dioxide, water, various mineral salts (principally constituents of nitrogen, calcium , potassium and phosphorus)- as well as vitamins and hormones. To satisfy these needs, plants have perfected strategies related to the varied environments that they have been able to colonize.
In particular, we often find carnivorous plants growing in acid soils (peat bogs) or in acid waters that are poor in mineral salts. In order to survive in these impoverished habitats, the carnivorous plants have devised traps that are the result of several thousand years of evolution. The prey captured and assimilated by these traps supply vitamins and proteins that plants living in richer soils take in through their roots in the form of mineral salts. Experiments with carnivorous plants have shown that fertilizers of whatever sort can in no way replace the nutrition contriuted by the captured insects, if one wants to obtain vigorous , flowering plants.
Carnivorous plants have been the source of many legends. If a young bird or small rabbit can be digested in the urn of a Nepenthes, why cannot a carnivorous plant be capable of capturing a man? A number of books , based on the accounts of explorers who cared little for scientific truth, have developed this theme. Thus at the end of the last century, there was talk of the 'man-eating tree of Madagascar', as terrifying as it was mythical.
Ancient botanical treatieses and pharmacopoeias attribute various properties to the sundews, or Drosera, whose red droplets of mucilage do not dry out in the sun. Certain extracts of these plants serve as treatment for corns, verrucas and burns. Infusions and other extracts were used against coughs, respiratory disorders, tuberculosis, arteriousclerosis, inflammations, intestinal illnesses, and syphilis. These preparations were diuretic, soothing and even aphrodisiac. Today extracts of Drosera are still used against coughs and ailments of the respiratory tract. The large-leaved butterwort, or Pinguicula was used to treat wounds. It was, and is, also used in the production of various cheeses - its leaves can, because of their high acidity, curdle milk.. Leaves of these plants feel greasy, hence the name Pinguicula which is derived from Latin, meaning fat and small. The fungal odor of Pinguicula is believed to be a prey attractant. Insects are trapped when they light or crawl on the surface of the leaves which are coated with a sticky mucilage. Only the smallest insects can be captured. The margins of the Pinguicula leaves tend to curl up during and after prey capture to form a shallow bowl which contains the digestive fluids and prevents loss of prey. Often the leaves tend to become distended beneath the spot where larger insects have been trapped.
The natives of certain tropical regions dare not, even today, touch Nepenthes, fearing the evil powers the plants are supposed to possess. Nepenthes are, though, used medicinally in a variety of ways. The liquid contained in the young urns before the operculum opens is an astringent and it seems also to have the property of soothing sore throats, inflammations and disorders of the skin and eyes. Extracts of the boiled roots have been used against dysentery and stomach complaints and the whole plant is used in various homeopathic preparations.
As mentioned, the carnivourous plants are comprised of 7 families namely: