On the cover: Phloem development is not easily followed in situ. Bauby et al. (in this issue, pages 97-109) succeeded in demonstrating the process of phloem development using Confocal Laser Scanning Microscopy. The cover photograph shows optical longitudinal section of aniline blue-stained hypocotyl of a 24-h-old Arabidopsis thaliana seedling (Ws ecotype). At this stage, protophloem precursors start to differentiate according to a gradient of differentiation from the upper part of the hypocotyl to the root. Bone-shaped differentiating protophloem cells can be clearly recognized by their bright fluorescence due to nucleus loosening and by the darkening of their outline due to cell wall thickening.
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