The anatomy of the bark of Agathis, Libocedrus, Dacrydium and Phyllocladus in New Zealand

Abstract

The anatomy of the bark of Agathis, Libocedrus, Dacrydium and Phyllocladus in New Zealand is described. Samples were collected from local areas in Canterbury, Buller and Northland, and examined by optical and scanning electron microscopy. In Libocedrus species, the sclerenchyma consists of thin and thick-walled fibres. In all other species, the sclerenchyma comprises fibres and sclereids. However, sclerenchyma is quite rare or sometimes absent in Dacrydium laxifolium. Crystals occur in the lumina and also in the wall (in the region of the middle lamella) of some phloem cells. Resin canals are present in the phloem, primary cortex and phelloderm of Agathis australis and in the primary cortex of all the three species of Phyllocladus. L and T-shaped parenchyma cells were found to be common in the phloem of Dacrydium cupressinum. These cells lie partly in the ray system and partly in the axial system, and are filled with tannin. Trabeculae were very common in the phloem in Libocedrus bidwillii. Phellem cells in Libocedrus species are very thin-walled and appear flimsy. In Agathis australis, the phellem cells are mostly thin-walled, with the outer 1-3 layers being thick-walled. Those in Dacrydium cupressinum, Phyllocladus glaucus and Phy. trichomanoides are all thin-walled. Phellem of the other six Dacrydium species consists of thin-walled cells and also cells with an inner tangential wall that is thicker than the outer tangential wall. In three species, this inner tangential wall is sclerified and in the other three species, it is non-polylamellate but possesses cone-shaped structures, protruding into the lumina. This latter feature is also shared by phellem cells in Phyllocladus alpinus. Minute crystals were found to be very abundant in the walls of phelloderm cells under lenticels, in most species.