Pine tree needle. Polarised light micrograph of a cross-section through a needle from a Pinus pine tree. This leaf is needle-like in order to reduce water loss (transpiration). The epidermis (deep green) consists of thick-walled cells covered with a layer of cuticle (red). Below the epidermis is the mesophyll (green and orange), which includes the resin canals (green and red circles). The central oval is the vascular cylinder, surrounded by the endodermis (white). Magnification: x195 when printed at 10 centimetres across.