The chemical characteristics of lignin in the differentiating xylem were investigated and compared with those of mature-wood. The compound middle lamella lignin deposited in the early stage of lignification of cell walls in the softwood(Larch) as well as the hardwood(Birch) was confirmed to be the so-called guaiacyl-type lignin and was found to have a relatively larger content of phenoxy hydroxyl group as terminal units and to be more abundant in condensed-type structures like as phenylcoumaran structures compared with mature-wood lingin.