ABSTRACT
Vegetative regeneration is a common strategy occurring in trees and shrubs, as is illustrated by the proliferation of adventitious shoots from the rootstock of the coastal, fire-tolerant conifer Sequoia sempervirens (Coastal Redwood). In Salix sp. (Willow), cane cuttings are frequently planted on the margins of lakes, where they quickly take root to form small bushes, which help to stabilise the shoreline. The details of ovule development and subsequent maturation in flowering plants and gymnosperms differ considerably. In gymnosperms, the ovule is naked and the embryo (as in Pinus) remains exposed on the tree during its subsequent maturation. By contrast, in flowering plants, the fertilized ovule and developing embryo remain hidden within the carpel. In some gymnosperms, the sexual organs are borne in massive cones, as shown in the tropical Australian female cycads Macrozamia fawcettii and Lepidozamia peroffskyana, the large, brightly coloured ovules of which are highly toxic for human consumption.
