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Plant druse crystal, SEM
Coloured scanning electron micrograph (SEM) of freeze-fractured plant tissue to show druse crystals. Druse crystals are a common occurrence in many plants and are usually granular or star-like in shape. Crystal formations that appear needle- or spear-shaped are referred to as raphides. Both are thought to deter herbivory, and a number of species of plants are poisonous to humans, as well as animals, due to the high calcium oxalate content. Even a small dose of calcium oxalate is enough to cause intense sensations of burning in the mouth and throat. The crystal's effects or symptoms may last for a week or more. Magnification: 1, 500X when printed at 10 centimetres wide.
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