Ginkoopsida descriptions

Ginkgoaceae Engler

Common names:

Ginkgo, maidenhair tree,

[Chinese].

Taxonomic notes:

The ginkgo is monotypic; this treatment presents sundry information for the Class Ginkgoopsida, Order Ginkgoales, Family Ginkgoaceae, and Genus Ginkgo. For the species, go to Ginkgo biloba.

Description:

Deciduous, dioecious trees. Bark gray, furrowed, with flattened ridges. Long shoots and short (spur) shoots present. Roots fibrous to woody. Leaves simple, flattened, fan-shaped, alternate to fascicled, stomata ventral, apex deeply cleft to truncate; petioles equal to or exceeding blades; resin canals absent; with numerous parallel veins; epidermis usually without exothecium. Pollen cones borne on spurs, elongate, catkin-like; sporophylls distributed along axis; bracts absent; pollen spheric. Seed cones absent; ovules 2, borne on spurs, pedunculate, subtended by collar believed to comprise 2 modified megasporophylls, orange-yellow, fleshy, pulpy, maturing in one year. Seeds with fleshy outer coat, inner coat hard, thin-shelled, wingless; cotyledons 2-3 (1, 2).

Range:

Native to China, but widely cultivated; see below for details.

Remarks:

Ginkgo differs from all other seed plants except Cycadales in having a distinct mode of fertilization by motile or free swimming sperm. Fertilization is usually by wind pollination (2).

Ginkgo is often referred to as a 'living fossil' because nearly identical plants are known from fossils nearly 200 million years old (1). The fossil record shows that they were formerly a widespread, abundant and diverse group.

Citations:

(1) R. David Whetstone in Flora of North America online.
(2) Silba 1986.