Vessel areas and distributions in Eucalyptus globulus and E. nitens vary in a consistent, significant and predictable way from pith to bark and within annual rings. Trends in vessel areas and distributions can be quantified despite the presence of indistinct annual rings and false rings. There is evidence of a vessel free area in first earlywood in E. nitens in which fibre properties are predictably different. At 5% height the vessel free area in the 1991 and 1992 annual rings is 13% and 1O% respectively.

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SummaryThe technique of animal vascular perfusion fixation was adapted for in situ fixation of the fragile and difficult to access cells of the ray parenchyma system in stems of 10-year-old Eucalyptus nitens trees. In situ fixation enabled tissue to be safely dissected for histological processing without risk of damage to microstructure or initiation of wound response. Fixative was perfused through the active vascular system under hydrostatic and transpiration pressure directly to vesselassociated ray cells. Diffusion from vessels allowed fixative to access nonvessel-associated ray cells. Acrolein was included to aid diffusion fixation and safranin dye was included to define fixed regions within the xylem. Sections prepared for light and electron microscopy from samples cut from regions showing intense safranin staining showed good microstructural preservation and were free of artefacts caused by mechanical injury or wound response.

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