Insectivorous Plants

Press, Volume CIX, Issue 32303, 22 May 1970, Page 10

Insectivorous Plants

Of all the various insectivorous plants that exist, the pitcher plants are probably the best known. Of these the sarracenias are the most familiar in cultivation. The species of sarracenias, perennial herbs of North America have such alternaAmerica, have such alternative common names as Indian cup, side-saddle flower, trumpet cup and huntsman’s horn. .They possess radical tubular | pitcher-shaped leaves and drooping, single stemmed flowers. A sugary secretion is exuded from the mouth of the pitcher. This acts as a lure to unwary insects which may then venture into the tube. Once within the pitcher they meet a belt of reflexed hairs which facilitate their descent into a watery fluid that lies at the base, and at the same time prevents their escape. The Malaysian region is the main habitat of the very perfect pitchers of the genus nepenthes which have a very powerful digestive action on nitrogenous matter. Cephaloties, which occurs in southIwest Australia, also has a form of trap arrangement for catching unwary insects. New Zealand is the home of a semi-aquatic family, the Utricularia, of which there are six species called collectively bladderworts. These plants are found in some of the swampy areas in different parts of both islands. They do not possess true roots and are generally found floating in the water. The submerged stems or branches bear small bladderlike structures, obviously

• modified leaves. The bladders, 1 e which are hollow, have an ) opening by means of which e small aquatic insects and t other minute organisms can enter. Examination of these traps usually reveals a coni siderable quantity of water - life in various stages of de- ■ composition. i Lack of oxygen within the • bladder accounts for the . fact that insects, once inside, r seem unable to get out again, 1 and thus die and decay where! 1 caught. The interior of the bladder is furnished with: 5 peculiar cells on short stems' ; the function of which is to absorb matter. Apart from their carnivorous habit the bladderworts are , unique in their mode of pol--5 lination which. although t adapted for cross pollinas tion where possible, can re- » adjust if necessary to assure pollination through self-pol- ! a lination.