Gum arabic. Samples of gum arabic, a resin taken from two species of the acacia tree (Acacia senegal and Acacia seyal). The gum is released by the trees to reseal the bark when it is damaged. Gum arabic is used in the food industry as a stabiliser and fixative and also as a vegetarian alternative to gelatin. Photographed at the Trotter Tripolitanian herbarium, Italy.