Rhyniophyta (rĪˌnēŏfˈətə) [key], division of plants known only from fossils, of which the genus Rhynia was perhaps the most important. These plants date from the Silurian and Devonian age. Relatively simple in structure, they resemble the Psilotophyta in many features, such as the lack of clearly developed roots. Like modern higher plants the Rhyniophyta had the specialized conducting tissues xylem and phloem. The Rhyniophyta are the most primitive group of vascular plants so far known and appear to be ancestral to most of the major divisions of vascular plants.