Almost all species of bamboo have hollow stems divided into nodes or joints. The stem can be up to 30 cm (a foot) in diameter. Each of the nodes has one side bud. Not all of those buds develop into branches, but some do. This makes bamboo one of the few grasses that have a branch structure. Bamboo rarely flowers. Some species only flower once, and then die off. The distance of two joints in a bamboo is the basis of a traditional Japanese unit of measurement, "shaku".