cross section: Larrea magnification: 100x common name: Creosote

The leaves of Larrea show numerous structural adaptations that extend their tolerance to drought and desiccation.

The epidermis consists of a single layer of small compact and heavily cutinized cells. Most epidermal cells contain dark staining deposits of waterproofing resins. Long epidermal hairs and stomata are present over the entire leaf surface. Stomata are roofed by epidermal cells with ledge like extension of cutin and overlay large substomatal chambers.

Two or three rows of tightly packed palisade mesophyll are present below the adaxial and abaxial epidermis. Spongy mesophyll is reduced to a narrow central band that supports the vascular bundles. In some preparations resins may be seen lining the stomatal cavities and coating the outsides of palisade cells. Idioblasts containing crystals of calcium oxalate are abundantly distributed through both mesophylls.

Small, centrally located vascular bundles span the breadth of the leaf. The bundles are collateral and closed with xylem of vessels and tracheids towards the adaxial(upper) surface and phloem of sieve tubes and companion cells towards the abaxial (bottom) surface. Cambium is not present.