A leaf is defined as an expanded organ, usually green, borne on the stem of a plant. Typically a leaf consists of an expanded blade (lamina) and a supporting stalk (petiole) but in many orchids the stalk is absent and the base of the leaf extends around the stem as a sheath. Small leaves are easily confused with bracts. In this key a bract is regarded as a reduced modified leaf associated either with an individual flower (fertile or floral bract) or arising on the peduncle (sterile bract).