A transverse section of a tree of this class shows it to consist of three distinct parts: the pith or medulla, the wood, made up of annual rings or layers, and the bark.
In the Araucarian type of wood (Araucaria and Agathis) the bordered pits, which occur in two or three rows on the radial walls of the tracheids, are in mutual contact and polygonal in shape, the pits of the different rows are alternate and not on the same level; in this type of wood the annual rings
annual rings与发音含义,同义词,反义词,翻译,刑和更多的