SEM Studies of Two Riparian New-Caledonian Conifers Reveal Air Channels in Stem Wood; Field Observations

Two New Caledonian conifers, Dacrydium guillauminii and Retrophyllum minor, both of Podocarpaceae, occupy distinctive habitats in which roots are characteristically inundated. SEM studies of stem wood anatomy of both reveal characteristic vertical intercellular channels, not apparent in light microscope examination. These channels are regular in spacing as seen in radial sections and indefinite in vertical extent; they were observed only adjacent to rays. These channels, not reported in other conifers, are a potential source of aeration for roots and submersed stem portions. Other wood details are reported. In order to provide a more comprehensive picture of adaptation to these habitats, observations based on field work are provided: these conifers are not only adapted to little-varying inundation of stems and lower roots, they are subjected to much greater sunlight than are upland conifers of New Caledonia.