Along the San Marcos River, in and surrounding Palmetto State Park in south central Texas, lie more than five square kilometers of relict ecosystem known as the Ottine Wetlands. This rich and fascinating area of swamps, marshes, and ponds is situated on the biogeographical divide separating the eastern plants and animals of the United States from their western counterparts, and also along a similar ecological boundary separating subtropical species from their more northern, temperate counterparts. Catalogued are more than 500 species, ranging from mosses and liverworts to flowering plants. Photographs and detailed descriptions aid in field recognition of more than 275 species; checklists are provided for those not treated in the text. An introductory chapter covers the regions geology and soils, climate, postglacial history, plant communities, and biogeography and also serves as a guide to Palmetto State Park and its easily accessible nature trails. Scientific researchers and nature enthusiasts alike will appreciate this expert guide to one of the nations most distinctive ecosystems.