Tannin Cells in Sparganium
cross section: Sparganium stem
common name: burr reed
The cells of the single layered epidermis have thickened outer walls and are overlaid with a well-developed cuticle. Numerous stomata are regularly spaced over the epidermal surface.
A narrow outer cortex of several layers of densely packed photosynthetic parenchyma cells is bound on its inner and outer edges by small radially arranged bundles of thick walled sclerenchyma cells.
The large inner cortex consists of a net like aerenchyma, interspaced with large radially arranged air pockets.
Well developed vascular bundles are found at the intersections the aerenchym strands. Because of this arrangement a central vascular stele is absent.
Within each vascular bundle proto and metaxylem are arranged in a V shape with phloem situated in between and above the metaxylem. A protoxylem lacunae is usually formed. The closed vascular bundles are wrapped in a bundle sheath of thick walled sclerenchyma cells. Vascular cambium is absent preventing the formation of secondary tissues.