The glassworts are various succulent, annual halophytic plants, that is, plants that thrive in saline environments, such as seacoasts and salt marshes. The original English glasswort plants belong to the genus Salicornia, but today the glassworts include halophyte plants from several genera, some of which are native to continents unknown to the medieval English, and growing in ecosystems, such as mangrove swamps, never envisioned when the term glasswort was coined. The common name "glasswort" came into use in the 16th century to describe plants growing in England whose ashes could be used for making soda-based (as opposed to potash-based) glass. Industrial uses The ashes of glasswort plants, and also of their Mediterranean counterpart saltwort plants, yield soda ash, which is an important ingredient for glassmaking and soapmaking. Soda ash is an alkali whose active ingredient is now known to be sodium carbonate. Glasswort and saltwort plants sequester the sodium they absorb from salt water into their tissues (see Salsola soda). Ashing of the plants converts some of this sodium into sodium carbonate (or "soda", in one of the old uses of the term). In the medieval and early post-medieval centuries, various glasswort plants were collected at tidal marshes and other saline places in the Mediterranean region. The collected plants were burned. The resulting ashes were mixed with water. Sodium carbonate is soluble in water. Non-soluble components of the ashes sank to the bottom of the water container. The water with the sodium carbonate dissolved in it was then transferred to another container, and then the water was evaporated off, leaving behind the sodium carbonate. Another major component of the ashes that is soluble in water is potassium carbonate, a.k.a. potash. The resulting product consisted mainly of a mixture of sodium carbonate and potassium carbonate. This product was called "soda ash" (it was also called "alkali"). It contained 20% to 30% sodium carbonate. For glassmaking, it was superior to a potash product obtained by the same procedure from the ashes of non-salty plants. If plant ashes were not washed as just described, they were still usable in glassmaking but the results were not as good. The appearance of the word glasswort in English is reasonably contemporaneous with a 16th-century resurgence in English glassmaking, which had suffered a long decline after Roman times. This resurgence was led by glassmakers who emigrated to England from Lorraine and from Venice. The Lorraine glassmakers brought