Fig. 6

Light micrographs show the formation of phloem wedges that preserve a continuous cambium (Ontogeny I). All sections were double-stained in safranin and Astra-blue. A–D Development of the stem of Mascagnia sepium. A Onset of development with regular secondary growth. B Shallow arcs of phloem are formed approximately 6 to 8 shallow arcs are visible. C Phloem arcs get deeper and turn into phloem wedges, some deeper than the others, given their different time of onset formation. D Adult stem with deep phloem wedges that furrow the xylem, some deeper than the others. E Mezia mariposa phloem wedges (arrowheads). F Peixotoa sericea with phloem wedges with different stages of development, some deeper than others (yellow dotted line and arrowheads), phloem wedges match with outer depressions of the stem (black arrowhead). G Niedenzuella multiglandulosa cambium is continuous throughout the phloem wedge (Pw), evidenced by the formation of inclined cells of phloem and xylem (yellow dotted lines and arrowhead). H M. sepium showing the formation of xylem and phloem perpendicularly to the previous tissues formed in the stem (yellow dotted lines and arrowhead), evidencing that the cambium is continuous, i.e., delineates the entire phloem wedge (Pw). I Mascagnia divaricata variant cambium produces under the phloem wedges (Pw) larger bands of non-lignified parenchyma (nlp) (arrowhead) than regular cambium. J Peixotoa sericea xylem under the phloem wedge (Pw) contains fewer vessels and more fibers, phloem wedges match with outer depressions of the stem (black arrowhead). K Mascagnia sepium parenchyma proliferation (pa) under the phloem wedges (Pw) proliferates (arrowhead) breaking up the inner xylem, stimulating proliferation also of the pith (p), in a continuum. Scale bars A–C, I–J = 1 mm, D = 5 mm, E, F = 200 µm, G, H = 400 µ, K = 500 µm