The vascular cambium usually, if not always, has a dual origin within the primary tissues; from provascular strands, and from the "ground" meristem tissues between those strands. These two modes of origin are termed intrafascicular (within fascicles) and intrafascicular (between fascicles). The term "provascular tissue" will be used in the text. We should know what this means. Provascular tissue is the precursor of all vascular tissues and "Procambium" is that part of the provascular tissue which is the precursor of the vascular cambium (which might as well also produce some metaxylem). The transitional stages between procambium and cambium are denoted as meta cambium. Both procambium and then meta cambium differentiate acropetally within the provascular bundles. If we see the transections of Populus, metacambium can be 1st detected via a series of radial, anticlinal divisions in across extended sets of tangentially aligned cells. Several divisions in this layer are periclinal, generating metaxylem and metaphloem. The cells among the metaxylem and metaphloem eventually start to function as cambial initials.