22.4: Cycads and Ginkgos

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Ginkgos (1 extant species)

As of writing this manual, the most recent genetic studies have placed Ginkgos as the oldest of the extant gymnosperms. This does not mean that it was the first gymnosperm. From the fossil record, it seems that most early gymnosperms went extinct. The sole remaining species in this group, Ginkgo biloba, is a living fossil virtually unchanged from its fossilized ancestors. It is possible that this species was only kept alive due to cultivation efforts by Buddhist monks for its medicinal properties. This species is also long-lived, a single tree can live for thousands of years, and resistant to most pests. Ginkgo biloba can be recognized by the following features:

Leaves deciduous, but tough, fan-shaped
Dioecious (di- meaning two, oecious meaning house), with male and female strobili on separate plants. Females plants have paired ovules at the tips of branches, males have catkin-like structures that produce pollen.
Wind pollinated

Observe the Ginkgo biloba specimens available in lab. Make notes and drawings of features that would help you recognize this species in the space below:

Cycads (approximately 300 extant species)

Cycads are another of the more ancient gymnosperm lineages, appearing in the fossil record around 300 million years ago. Currently, many extant species are in danger of extinction in the wild. However, during the Jurassic period, these plants would have dominated the landscape. Though their large, compound leaves make them appear to be ferns at first glance, cycads can be classified as gymnosperms by the production of seeds instead of spores and xerophytic leaves. These plants share the following features:

Dioecious. Male and female strobili on separate plants.
Large compound, xerophytic leaves
Insect pollinated

Observe the cycad specimens available in lab. Make notes and drawings of features that would help you recognize this group in the space below:

Contributors and Attributions

Maria Morrow (College of the Redwoods)