Taxa of seed plants represented by one living species, Ginkgo biloba. This species is restricted to China where it may be extinct in the wild. The group was well represented during the Mesozoic with worldwide distribution. Today, Ginkgo biloba is widely planted as an ornamental. It is especially useful as a street tree as it is tolerant of city polluted air.
Vegetative Characteristics: Deciduous trees bearing distinctive fan-shaped leaves. Branches with numerous spur shoots that bear the reproductive structures. Stems with extensive secondary growth producing considerable secondary xylem.
Reproductive Characteristics: Dioecious trees. Megasporangiate trees bearing two ovules at the end of a stalk. Typically only one ovule develops into a mature seed. Integument includes three layers. The inner layer develops into the stoney seed coat. The outer two into a fleshy fruit-like tissue. Because this tissue has a strong, unpleasant odor, "male" buds are typically grafted onto seedling roots to produce "male" trees for ornamental use. Microsporangiate ("male") trees bear catkin-like microsporangiate strobili. These release pollen (microgametophytes) that are wind borne. Pollen produces a pollen tube that is haustorial and which delivers flagellated sperm to an egg in an archegonium of the female gametophyte.