Fig. 3
Development of successive cambia in stems of Leucaster caniflorus and Ramisia brasiliensis (ontogeny 2). A–C Leucaster caniflorus. A Young stem with regular eustele. B Initiation of secondary growth through the extra-fascicular cambium (thick black arrows); note the first formed vessels of the secondary xylem (thin black arrows). C Detail of the extra-fascicular cambium (thick black arrows) and first formed vessels (thin black arrows); note the pericycle parenchyma cells (asterisks). D, E Ramisia brasiliensis. D Establishment of the extra-fascicular cambium (thick black arrows) outside the vascular bundles of the eustele. E Secondary vascular tissue (double arrow) originated from the extra-fascicular cambium (thick black arrow). The yellow arrow indicates a vessel element, and the red arrow indicates a sieve-tube element and its companion cell. Note the developing meristematic zone (white arrows) undergoing cell divisions that will give rise to the subsequent ring of successive cambia. The conjunctive parenchyma is also observed. Scale bars: 100 μm (A, B, E); 50 μm (C); 400 μm (D). ct conjunctive parenchyma, pe pericyclic fibres, pi pith, ra ray, vb vascular bundles of the regular eustele. A–E Stained with toluidine blue