Warts have been observed in several bamboo species; they are present not only in vessel members and fibres, but also in the highly lignified parenchyma cells, especially in those of the elongated type. Among the 34 species studies only a few possess warts in all three cell types. The sizes of warts lie within the range observed for dicots and gymnosperms. There is no recognizable correlation between the occurrence of warts and the taxonomic grouping of bamboos. It has been suggested that the development of warts is associated with the lignification of the cell wall.