Genlisea is a genus of about 30 species of carnivorous plants commonly known as corkscrew plants, and are found in tropical Africa, Madagascar, and South America. Corkscrew plants can be found growing in wet terrestrial to semi-aquatic environments, and use their modified underground leaves to attract, trap and digest prey, which are typically protozoans.
Genlisea are small herbs with two types of leaves, the above-ground photosynthesis foliage leaves and the highly modified subterranean leaves that trap preys. Besides trapping preys, the subterranean leaves also function as anchorage and water absorption, as the plant lacks roots. The 0.5-5 cm long, linear to spatula-shaped foliage leaves grow in small, and compact rosettes, with most of the leaves, including the petiole, is hidden beneath the soil. The rosette can grow up to 5 cm wide. The subterranean leaves are lacking chlorophyll and appear as pale bundles of root-like organs, and can grow up to 15 cm long.
The top part of the subterranean trap consists of a descending stolon, and about midway down the stolon, there is a swollen digestive chamber or utricle. Below the chamber, the stolon continues downwards as a hollow tube. The tube bifurcates into two long, spiraling branches. Each branch is spirally-slit along its length, with the opening acts as the trap entrance. The inside of the spiraled trap arms, and the hollow cylinder section leading from the bifurcation to the utricle, are lined with inward pointing hairs. The intricate, curved hairs ensure that the chemically-attracted prey can only move in one direction and towards the utricle.
The yellow to violet flowers are borne in a group of 1-11 at the apex of tall inflorescence, up to 40 cm tall. The flowers are typically 1.5-2 cm long.
Some species produce two types of traps on the same plant- smaller ones confine to near the soil surface, and much larger ones that penetrate deeply into the soil.
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Denis Barthel
