The terms cambial cell, cambial fiber, mother cell, and tissue mother cell were often employed in a nonspecific sense with reference to the cambium by early investigators. At times, one of these terms might be confined to the dividing cell(s), and at other times it might include derivative cells. The nonspecificity of the terms was due mainly to difficulties in isolating the cambium for microscopic observation, consequently, to difficulties in formulating a precise definition.