Cycas and Ginkgo are regarded as living fossils because most of their close relatives have extinct which flourish well in Jurassic period of the Mesozoic era. Nine living genera and about 100 species are included in order-Cycadales, while order-Ginkgoales includes only one species called Ginkgo biloba which occurs in the living state. This species is known as living fossil. Cycas is a heterothallic plant and its species are strictly dioecious and either male cones or megasporophylls are formed on a plant. Ginkgo is also dioecious, the male and the female structures are axillary in position.