Sapwood

sapwood, also called alburnum, outer, living layers of the secondary wood of trees, which engage in transport of water and minerals to the crown of the tree. The cells therefore contain more water and lack the deposits of darkly staining chemical substances commonly found in heartwood. Sapwood is thus paler and softer than heartwood and can usually be distinguished in cross sections, as in tree stumps, although the proportions and distinctness of the two types are variable in different species.