FIG. 6 in Bark anatomy of lianescent Bignoniaceae: a generic synopsis

FIG. 6. — General features of the variant phloem; A, Adenocalymma alboaurantiacum transverse section (TS), variant phloem located in the phloem wedges (Pw), and regular phloem located in the interwedges (Iw). Fibrous phloem, sieve tubes generally in multiples, sometimes solitary. Ray dilatation occur very soon in the regular phloem, while it only occurs in the outermost parts of the phloem wedge (arrows); B, Bignonia magnifica, TS, non-fibrous phloem, with a series of concentric fiber bands, alternating with a large amount of sieve tubes and axial parenchyma cells. Thin fiber bands, up to 3 cells in width, surrounded by acicular crystals (seen as beige deposits). Sieve elements solitary or in multiples, p-protein visible at sieve plates (arrows), one companion cell per sieve tube. Whenever a sieve tube is lying next to a ray, its companion cell faces it; C, Pleonotoma tetraquetra, TS, fibrous phloem, sieve tubes solitary or in multiples of 2, sieve-tube centric axial parenchyma, fibers square to rectangular; D, Bignonia magnifica longitudinal tangential section (LS), sieve tubes longer than 500 μm, with p-protein accumulated at the sieve plates. Rays uni to biseriate. Axial parenchyma with 3-4 cells per strand; E, Callichlamys latifolia, LS, rays uni to biseriate, non-storied; F, Callichlamys latifolia, TS, definitive callose deposited in the sieve plates (arrows). No collapse of cells in fibrous phloems; G, Pachyptera aromatica, TS, sieve tubes eventually collapse in non-fibrous phloems (arrows); H, Bignonia magnifica, LS, starch accumulation greatly increases in nonconducting phloem. Scale bars: A, 500 μm; B, E, 200 μm; C, D, G, H, 100 μm; F, 50 μm.