London, 1894); Hirase, Etudes sur Ia fhcondation et lEmbryogenie du Ginkgo biloba, Journ.
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).
The Cordaitales (see Palaeobotany: Palaeozoic) are represented by extinct forms only, which occupied a prominent position in the Palaeozoic period; these plants exhibit certain features in common with the living Araucarias, and others which invite a comparison with the maidenhair tree (Ginkgo biloba), the solitary survivor of another class of Gymnosperms, the Ginkgoales (see Palaeobotany: Mesozoic).
- This class-designation has been recently proposed to give emphasis to the isolated position of the genus Ginkgo (Salisburia) among the Gymnosperms. Ginkgo biloba, the maidenhair tree, has usually been placed by botanists in the Taxeae in the neighbourhood of the yew (Taxes), but the proposal by Eichler in 1852 to institute a special family, the Salisburieae, indicated a recognition of the existence of special characteristics which distinguish the genus from other members of the Coniferae.
Ginkgo biloba, which may reach a height of over 30 metres, forms a tree of pyramidal shape with a smooth grey bark.
Ginkgoales; Hirase, " Etudes sur la fecondation, &c., de Ginkgo biloba," Journ.
(1898); Seward and Gowan, " Ginkgo biloba," Ann.
(1900) (with bibliography); Ikeno, " Contribution a l'etude de la fecondation chez le Ginkgo biloba," Ann.
(1901); Sprecher, Le Ginkgo biloba (Geneva, 1907).