Bur

rdf:langString Bur

rdf:langString A bur (also spelled burr) is a seed or dry fruit or infructescence that has hooks or teeth. The main function of the bur is to spread the seeds of the bur plant, often through epizoochory. The hooks of the bur are used to catch on to for example fur or fabric, so that the bur, which contain seeds, then can be transported along with the thing it attached itself to. Another use for the spines and hooks are physical protection against herbivores. Their ability to stick to animals and fabrics has shaped their reputation as bothersome. Some other forms of diaspores, such as the stems of certain species of cactus also are covered with thorns and may function as burs. Bur-bearing plants such as Xanthium species are often single-stemmed when growing in dense groups, but branch and spread when growing singly. The number of burs per fruit along with the size and shape can vary largely between different bur plants.