Samples of dormant and of actively growing cambial-zone tissue collected in June and March, respectively, from plantations of young white spruce (Picea glauca [Moench] Voss) and red pine (Pinus resinosa Ait.) near Ottawa, Canada, were fixed in five different solutions at three temperatures. Fixation quality was evaluated by electron microscopy.Not all cellular organelles were preserved equally well by the same fixative in the active and in the dormant conditions, or in both spruce and pine. In general, our best results were obtained with Karnovsky's fixative solution. Somewhat less satisfactory results were obtained with a glutaraldehyde-acrolein mixture followed by straight glutaraldehyde. Poorer results were obtained with a trialdehyde solution while a glutaraldehyde-osmium tetroxide cocktail undoubtedly provided the worst fixation.Different fixative temperatures had a marked effect on fixation quality only when phosphate buffer was used. There was little gained by prolonging the period of fixation beyond a few hours
