Carnivorous plants

Most species are climbers, often several metres long. The midrib of the leaf is prolonged into a tendril, which forms a globe- or tube-shaped pitcher. Usually, two types of pitchers are produced, larger ones near the ground, and smaller ones higher up. The ‘lip’, or peristome, around the upper edge of the pitcher is very slippery, causing tiny animals to slide into the trap. The fluid in the pitcher is viscoelastic, causing winged insects to be unable to escape. Along the inner edge is a row of stiff, down-pointing hairs, which prevent prey from escaping. Above the peristome is an umbrella-like cover, the operculum, the purpose of which is to prevent excess rainfall into the pitcher.

This plant, also known as cobra plant, was discovered in 1841, and in 1853 it was described by American botanist, chemist, and physician John Torrey (1796-1873), who named it Darlingtonia, in honour of botanist William Darlington (1782-1863) of Philadelphia.

Fragrance from nectar, emitted by the plant, lures insects into the long, tube-shaped pitchers, which are filled with fluid.

About 120 species of butterwort are presently known, with the largest number found in Central and South America, while 12 species are native to Europe, 9 to North America, and a few to northern Asia.

The generic name is diminutive of the Latin pinguis (‘fat’ – compare the word ‘penguin’), which, like the common name butterwort, refers to the slimy and fatty leaves. This slime was applied to cracks in cow udders. On an excursion in 1747, an apprentice of Swedish naturalist Carl Linnaeus (1707-1778), says that ”in Switzerland, Pinguicula is used externally on fissuris mammarum, even if the udder becomes hardened, so that it will milk blood.”

Formerly, in large parts of northern Europe, a common practice was to apply leaves of butterwort to milk to make it separate or thicken. German farmers would place butterwort plants in water, later using this water to make tough or newly cut meat tender.

In folk medicine, the plant has mostly been used to heal wounds and various skin problems. In Denmark, in the 1900s, when many children were suffering from ringworm and other skin ailments, the affected parts were smeared with butter, or leaves of butterwort.

In his thesis from 1688, De usu plantarum, Danish herbalist Ole Borch recommends butterwort for treatment of ”hectica febris legitima [consumption] and hernia.” You must apply a compress of milk, he says, mixed with moss or butterwort roots on the affected parts, not only for healing, but also to give it back its natural humidity.

In the old days, in Denmark, farmers were convinced that if sheep would consume butterwort “before Michaelmas” (September 29), they would get liver flukes (Distoma hepaticum). However, the biological explanation is that the sheep got these parasites by grazing in wet areas, where not only butterwort thrives, but also the flukes.

Members of this genus capture small animals by means of bladder-like traps. The pressure inside the bladder is negative, compared to its surroundings. When trigger hairs on the trapdoor is touched by a tiny animal, the prey, along with the water around it, is sucked into the bladder, whereupon the door closes again, the whole procedure lasting only 1/10,000th of a second.

This genus contains aquatic as well as terrestrial species. Aquatic species catch larger prey like water fleas and nematodes, whereas terrestrial species catch tiny organisms like protozoa and rotifers.

Members of this genus obtain the major part of their nutrients by catching small invertebrates by means of glandular hairs on their leaves. When an animal gets stuck in the sticky juice from these glands, the leaf envelops the unfortunate victim, whereupon enzymes dissolve its body juices, making nitrogen and other nutrients available for the plant.

These plants are called sundew due to their sticky glandular hairs, which resemble dew drops, when the sun is shining on them. Formerly, in European folk medicine, dew drops were said to possess miraculous qualities, and the glandular ‘drops’ of sundew were sold as Virgin Mary’s tears. Supposedly, they were able to cure skin diseases like warts, ringworms, and corns, besides many other ailments.

In the old days, in Denmark, farmers were convinced that if sheep would consume sundew “before Michaelmas” (September 29), they would get liver flukes (Distoma hepaticum). The real cause for the sheep to get these parasites was that they were grazing in wet areas, where not only these plants thrive, but also the flukes.

It was described in 1759 by North Carolina governor Arthur Dobbs (1689-1765), who wrote: “But the great wonder of the vegetable kingdom is a very curious unknown species of sensitive; it is a dwarf plant; the leaves are like a narrow segment of a sphere, consisting of two parts, like the cap of a spring purse, the concave part outwards, each of which falls back with indented edges (like an iron spring fox trap); upon any thing touching the leaves, or falling between them, they instantly close like a spring trap, and confine any insect or any thing that falls between them; it bears a white flower: to this surprising plant I have given the name of ‘Fly Trap Sensitive’.”

Venus flytrap was highly praised by Swedish naturalist Carl Linnaeus (1707-1778), who called it a “miraculum naturæ”, and by British naturalist Charles Darwin (1809-1882), who labelled it “one of the most wonderful plants of the world.”

This species is unique among flesh-eating plants in having highly modified leaves, which act like a snap-trap, when stimulated in a certain way. On the inner surface of the trap are three stiff hairs, and two of these must be stimulated within a short period of time to trigger the trap. This mechanism has been developed to prevent the plant from using energy on shutting the trap, if e.g. a withered leaf by chance falls into it. Thick, stiff protrusions, or cilia, along the edge of the trap form ’bars’, which prevent prey from escaping.

Portuguese sundew is one of the few carnivorous plants, which is able to thrive on dry, alkaline soils. The leaves, which are 20 to 40 cm long, uncoil from a central rosette. The plant emits a sweet aroma, which attracts insects. When they land on a leaf, or on the stem, they get stuck in the numerous sticky glandular hairs.