Fig. 1

Terminology adopted for phloem wedges. A Stem with phloem wedges well-developed, two regions are identified: interwedges (Iw) and phloem wedges (W). Interwedges are the areas between phloem wedges and where the cambium maintains its regular activity. Phloem wedges are regions derived from a variant cambial portion that produces more secondary phloem and less secondary xylem. B Phloem wedge (W). Phloem wedges are commonly flanked by limiting rays (Lr), which are tall, wide multiseriate rays. C Phloem wedges well-developed with cambium disrupted. Mechanical pressure causes the inclusion of inner portions of wedges, known as interxylary phloem (Ip). D The transformation of flanking regions of the wedge from a regular to a variant activity causes wedges to have a stepwise pattern. Magenta dotted line outlines this pattern. Portions of the variant cambium (Cp) remain on the bottom of the wedges. Color key: black = pith limits, blue = secondary phloem, grey = dermal tissue, red = vascular cambium, orange = limiting rays