Scientists classify plants as bryophytes—nonvascular plants (see above)—or tracheophytes, which are vascular plants. They are represented by the seedless plants (such as ferns that reproduce by spores) and seed plants (separated into gymnosperms, or conifers, and angiosperms, or flowering plants). The word “vascular” comes from the Latin word vasculum, meaning “vessel” or “duct.” Members of the extinct genus Cooksonia—named for the paleobotanist Isabel Cookson (1893–1973)—were the first ancient vascular plants to be identified. (For more about early plants, see this chapter.)