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Plants and snails by Hugo de Vries

Hugo de Vries 1848-1935

Professor Ernst Stahl of Jena has researched the relationship between plants and snails and showed how the first are protected from the latter by different means.Stahl looked at snails in the wild as well at snails kept in captivity.These were kept in a glass bowl and made hungry.He gave them plants with their natural defense mechanisms and plants stripped of those.The snails always ate the plants stripped of the defense mechanisms first and only ate the plants with the defense mechanisms intact much later when they were hungry.The best mechanism is an unpleasant taste.Several chemicals cause this taste,tannin being the most important one. Acids ,essential oils,alcaloids and bitter tasting chemicals are also ways to deter snails. Pieces of carrots with a solution of 0.1 % tannin are eaten as much as fresh pieces.Pieces with a 1% solution are nibbled at but further left alone.A solution of 0.5 % sorrelacid is enough to make the carrots unedible. There is no doubt that these natural chemicals keep the snails from eating plants. The substance being secreted by hairy leaves and stems with glands is also unpleasant for snails. In the nature you will see snails eating from dying or rotten leaves because these donít have much tannin or other chemicals left. Another deterent for snails to eat a plant is toughness of leaves and stems.Silicic acid in leaves is a good way to protect them.Certain grasses have such hard leaves that even cattle wonít eat it. Many seaweeds are surrounded by a layer of jelly and very slippery.They slip between fingers as well as through the jaws of snails.Professor Stahl observed how the snails made fruitless attempts to eat those plants, driven by hunger. Raphides give parts of plants a burning taste,in roots of Arums this is very unpleasant.Leaves of Typha which Stahl gave to a young rabbit,made the animal so ill because of the raphides that it died. Plants which contain raphids are totally safe from snails no matter how tasty they may be. These examples are a good way to give you an image which methods plants use against snails.The methods are very diverse although the inside of plants is very much the same. In large groups of plants certain means of protection are prominent.These replace eachother or sometimes different methods appear on one plant together. Some examples are:silicic acid protects grasses and Equisetums;hard hairs the Asperifoliacids;raphides the Orchids, Arums and Lilies;tannins the ferns,the Papilionacaea,and the Ericacaea;essential oils the Labiates;alcaloids the Solanacaea. The diversity plants show us in this area is not finished with these examples. But this may be enough to make my readers alert to the relationship between plants and animals. And when you begin to notice these phenomena you will follow the movements of snails with greater interest.And thinking about Stahlís experiments you can explain many curiosities which meaning you otherwise wouldnít know.

Translated from a dutch article "Planten en slakken" which was published in the magazine Album der natuur,1889. (c)2003-this translation by Arno Brosi main page