On account of the resemblance of the leaves to those of some species of Adiantum, the appellation maiden-hair tree has long been given to Ginkgo biloba.
The endosperm detached from a large Ginkgo ovule after fertilization bears a close resemblance to that of a cycad; the apex is occupied by a depression, on the floor of which two small holes mark the position of the archegonia, and the outgrowth from the megaspore apex projects from the centre as a short peg.
The structure of the seed, the presence of two neck-cells in the archegonia, the late development of the embryo, the partially-fused cotyledons and certain anatomical characters, are features common to Ginkgo and the cycads.
The morphology of the female inflorescence of Cordaiteae has not yet been cleared up, but Taxus and Ginkgo among recent plants appear to offer the nearest analogies.
During the growth of the cell which forms the megaspore the greater part of the nucellus is absorbed, except the apical portion, which persists as a cone above the megaspore; the partial disorganization of some of the cells in the centre of the nucellar cone forms an irregular cavity, which may be compared with the larger pollen-chamber of Ginkgo and the cycads.
These six groups were the dominant types throughout the period, but during Upper Carboniferous time three other groups arose, the Coniferales, the Cycadophyta, and the Ginkgoales (of which Ginkgo biloba is the only modern representative).
Amongst Conifers the archaic genera, Ginkgo and Araucarus still persist.
This is not the place to discuss in detail the past history of Ginkgo (see Palaeobotany: Mesozoic).
Size.) characterized by a rather larger number of oval pollen-sacs on the stamens, have been found in England, Germany, Siberia and elsewhere in association with Ginkgo and Baiera foliage.
During the Triassic and Jurassic periods the genus Baiera - no doubt a representative of the Ginkgoales--was widely spread throughout Europe and in other regions; Ginkgo itself occurs abundantly in Mesozoic and Tertiary rocks, and was a common plant in the Arctic regions as elsewhere during the Jurassic and Lower Cretaceous periods.