Fig. 2

Single cambial variant or combination of two cambial variants of stem cross section. A Interxylary phloem (enlargement): Thunbergia grandiflora. B Intraxylary phloem (enlargement) combined with successive cambia: Distimake tuberosus. C Irregular conformation combined with axial vascular elements in segments: Tetrastigma obtectum var. glabrum. D External primary vascular cylinders combined with axial vascular elements in segments: Piper kadsura. E Furrowed xylem of cambium continuity combined with intraxylary phloem: Gymnema sylvestre. F Furrowed xylem of cambium discontinuity combined with axial vascular elements in segments: Clematis gouriana subsp. lishanensis. PI, pith, TE, interxylary phloem, TR, intraxylary phloem, 1st XY, first xylem, 2nd XP, second xylem, 1st PH, first phloem, RA, ray, XY, xylem, PH, phloem, SCL, sclenchyma, MU, mucilage canal, ME, medullary vascular bundles, PE, peripheral vascular bundles, FD, furrowed xylem of cambium discontinuity, FC, furrowed xylem of cambium continuity, PW, phloem wedges