bundle sheath mestome sheath PO:0006025 The inner endodermal sheath of a two layered bundle sheath. The cells are smaller in diameter compared to those in outer wall (starch sheath). The cell walls are thick and contain suberized lamellae. They are analogous to endodermis. plant_anatomy vaina del mestoma (Spanish, exact) メストム鞘、維管束鞘の内側、維管束鞘延長部 (Japanese, exact)