The Anthophyta, commonly known as the angiosperms, are flowering plants and include the trees, shrubs, herbs and grasses so conspicuous in the terrestrial environment. They are characterized by seeds which develop and ripen inside an ovary. While the vast majority are terrestrial, some live in freshwater ponds, lakes and rivers, but few are adapted to the marine environment. Of these, some are tolerant of periodic submersion in sea water and are often common on the shore, while others are tolerant of salt spray and are characteristic of the littoral-fringe–terrestrial boundary. The angiosperms included here tolerate daily submersion by the tide, and together with seaweeds such as Ulva (Enteromorpha) (p. 30), are important colonizing and stabilizing species of sand and mud deposits. Almost invariably, the presence of these plants slows down water movement, resulting in the deposition of fine particles and an increase in the level of the beach leading to a plant succession typical of saltmarshes and dominated by angiosperms such as thrift (Armeria maritima Willd.), sea aster (Aster tripoliumL.) and seablite (Suaeda maritima (L.) Dumort.); these are not included in this text. The three genera described below are readily identified and common on sheltered shores and estuaries.