Softwood anatomy: A review

Although conifers have very homogeneous wood anatomical structure, some of their features allow differentiation of genera or groups of genera. Softwood anatomy is reviewed and the authors have added contributions, grouping features in five blocks (axial tracheids, axial parenchyma, rays, resin canals and mineral inclusions), with special attention to their diagnostic value at the family, genus or species levels. The discussion addresses, in axial tracheids: growth rings, intercellular spaces, pit arrangement, presence of scalloped tori, torus extensions, notches, warty layer, organic deposits, helical and callitroid thickenings, bars of Sanio and trabeculae; in axial parenchyma: presence or absence, arrangement and type of transverse end walls; in rays: composition, type of horizontal and end walls and cross-field pitting; in resin canals: epithelium and the presence of normal or traumatic resin canals; and in mineral inclusions: presence or absence. Wood structure is characterised at the family level, discussing the main elements that can be used for diagnosis at the genus level or in groups of genera.