Horsetail family (Equisetaceae)

Horsetails were the dominating plants during the palaeozoic peroid. Today the family only contains 15 species of the genus Equisetum. The plants are characterized – like some grasses – by high contents of silicic acid. Therefore, field horsetail was used in former times as a cleaning agent for tin. The figure shows Equisetum fluviatile as an example.