Burs are seed cases that develop from certain plants, often featuring a spiky or prickly exterior. They serve as a protective covering for seeds, helping to ensure their survival and dispersal. When animals or humans come into contact with burs, they can easily attach to fur or clothing, facilitating the spread of seeds to new locations. Common examples of plants that produce burs include burdock and cocklebur. These plants have evolved this method of seed dispersal to increase their chances of germination in diverse environments. Burs can be found in various habitats, contributing to the plant's reproductive success.