Wood anatomy of Wollemi pine (Wollemia nobilis, Araucariaceae)

The wood anatomy of the recently-discovered conifer Wollemia nobilis (Wollemi pine) is described for the first time. Its mature heartwood is light brown in colour and has an air dry density of 0.57 g/cm³. Growth ring boundaries are distinct and the transition from earlywood to latewood is gradual. Average tracheid length is ∼ 3.4 mm. Bordered pits are one-, two- or three-seriate and the double and triple rows of pits are 'alternate'. In the bordered pits there is a flat transition from torus to margo. A warty layer lines tracheid walls and pit cavity surfaces. Resin plugs are common in tracheids that are adjacent to rays. Helical thickenings and crassulae are absent. Rays are uniseriate, low, and are composed entirely of parenchyma cells whose walls are thin and unpitted. Cross-field pitting is 'araucaroid' and the number of pits per cross-field ranges from 3-11 (av. 7). Resin canals and axial parenchyma cells are absent. The differences between normal mature wood compared to compression and juvenile wood are consistent with those of most other conifer genera. The anatomical features of wood of W. nobilis strongly support its classification as a member of the Araucariaceae, but show no major differences that distinguish it as a monotypic genus. On the basis of its wood anatomy, it is not possible to state whether W. nobilis is more closely related to Agathis or to Araucaria.