Bark anatomy of lianescent Bignoniaceae: a generic synopsis Author Pace, Marcelo R. Author Marcati, Carmen R. Author Lohmann, Lúcia G. Author Angyalossy, Veronica text Adansonia 2023 3 2023-05-30 45 12 167 210 journal article 10.5252/adansonia2023v45a12 1639-4798 8006364 X. Tanaecium clade TAXONOMIC INFORMATION . — This clade contains a single genus, Tanaecium , with four phloem wedges in transversal section and a single species, Tanaecium tetramerum (A.H.Gentry) Zuntini & L.G.Lohmann , that lacks phloem wedges and only shows a regular phloem. Tanaecium currently includes species from seven previously recognized genera ( Table 1 ), Arrabidaea , Ceratophytum Pittier , Pseudocatalpa A.H.Gentry , Spathicalyx J.C.Gomes, Sphingiphila A.H.Gentry , Paragonia Bureau , and Periarrabidaea A.Samp. TOTAL NUMBER OF SPECIES IN THIS CLADE . — 21 species ( Frazão & Lohmann 2019 ). STUDIED SPECIES . — Three species, Tanaecium bilabiatum (Sprague) L.G.Lohmann , T. pyramidatum (Rich.) L.G.Lohmann , and T. tetramerum (A.H. Gentry) Zuntini & L.G.Lohmann. Regular phloem Thin to thick fiber bands, assemblages generally present ( Fig. 13A ), but absent in T. tetramerum . Exclusively thin fiber bands occur in Tanaecium bilabiatum and T. tetramerum ( Fig. 13D ). Variant phloem General configuration. Semi-fibrous ( Fig. 13B, C ) to fibrous, with semi-fibrous species ( Tanaecium pyramidatum ) exhibiting fiber bands alternating with 4-8 rows of sieve elements and phloem parenchyma ( Fig. 13B, C ), and fibrous species ( Tanaecium bilabiatum ) showing a matrix of fibers that intermingle all other cells. The axial elements exhibit a diffuse to tangential arrangement ( Fig. 13B, C ). Sieve-tube elements. As seen in transversal section, each sieve element is associated with 1-2 companion cells ( Fig. 13C ). The sieve elements are generally solitary or in multiples of 2-3 cells ( Fig. 13C ). As seen in tangential section, the sieve elements are short (< 1 mm ) and their end walls are inclined, bearing compound sieve plates with 16-18 sieve areas. Axial parenchyma. The phloem parenchyma is sieve-tube-centric incomplete. In Tanaecium pyramidatum , the phloem parenchyma is much more abundant, also forming radial rows ( Fig. 13B, C ) that may be lignified in some portions ( Fig. 13B, C ), completely lignified in the nonconducting phloem. In T. bilabiatum , incomplete tangential rows may be found near the sieve elements. Fibers. In T. pyramidatum the fiber band has 1-2 rows of cells ( Fig. 13B, C ), while in T. bilabiatum the fibers form a matrix that intermingle all other cells. Rays. The limiting rays are lignified to both xylem and phloem faces, with a radial row non-lignified between them. The wedge rays have randomly alternating portions lignified and non-lignified ( Fig. 13B ). Crystals. Absent. Periderm A single periderm is formed. The phellem is stratified in Tanaecium pyramidatum and T. tetramerum , non-stratified and thin-walled in T. bilabiatum ( Table 2 ). The phelloderm is thick, with over three layers of cells, non-stratified. Lenticels were only observed in T. pyramidatum , non-stratified, with lignified filling cells ( Table 2 ).