Cross-Section of Eleutherococcus sp Stem (fragment) On the right there are well discernible periderm tissues: phellema, phellogen, phelloderma. Below there is collenchyma with thickened cell walls, parenchyma with calcium oxalate crystals, secretory cells and clearly visible vascular bundle tissues of the stem – xylem and phloem. The authorial prepared mount, polychrome painted tissues Light microscopy, bright-field in transmitted light