Young pine tree stem, light micrograph 照片檔

Young pine tree stem. Light micrograph of a section through a one year old primary pine (Pinus sp.). The cells of the outer epidermis (red) are thick-walled and covered with a thick layer of cuticle to prevent water loss. Beginning to form underneath the epidermis is the cork cambium (phellogen) which has produced 2 to 3 layers of cork (orange), this helps to resist forest fires. The vascular cylinder (centre) consists of a thin layer of phloem (blue) and first year xylem (red). Embedded in the xylem are scattered resin canals. The pith is at centre. Magnification: x20 when printed at 10 centimetres wide.