Ginkgo leaf stalk. Light micrograph (LM) of a transverse section through the leaf stalk (petiole) of a ginkgo tree (Ginkgo biloba). Ginkgo biloba, commonly known as ginkgo or gingko, also known as the maidenhair tree, is a species of tree native to China. It is the only living species in the order Ginkgoales, which first appeared over 290 million years ago. The outer epidermis surrounds the cortex, which consists of parenchyma cells with inter-cellular spaces and resin canals (white spacess) characteristic of gymnosperms. The kidney-shaped vascular cylinder (centre) is surrounded by a single-layer endodermis, inside which are the tracheid cells (red) of the xylem and the sieve cells (blue) of the phloem. Magnification: x14 when printed 10 centimetres wide.