Vessels are the integral component of the xylem. These are typically found in flowering plants (angiosperms) but absent from most of the gymnosperms such as conifers. Vessel elements are the main feature distinguishing the hardwood of angiosperms from the softwood of conifers. Gymnosperms are also called as 'softwood spermatophytes' because they lack thick-walled vessels rendering them softwood plants; because vessels impart strength to wood.