<P> Bur - bearing plants such as Xanthium species are often single - stemmed when growing in dense groups, but branch and spread when growing singly . </P> <P> Burs catch on the fur of passing animals or the clothing of people . The hooks or teeth generally cause irritation, and some species commonly cause gross injury to animals, or expensive damage to clothing or to vehicle tires . </P> <P> Burs serve the plants that bear them in two main ways . </P> <Ul> <Li> Firstly, burs tend to repel some herbivores, much as other spines and prickles do . </Li> <Li> Secondly, plants with burs rely largely on living agents to disperse their seeds; their burs are mechanisms of seed dispersal by epizoochory (dispersal by attaching to the outside of animals). </Li> </Ul>

Things that stick to your clothes in the woods